It was Little League baseball opening day, April 2004, somewhere in central Pennsylvania, and I was sitting cross-legged on the grass on the third-base side of the field. My 12-year-old son, Jamie, was sitting on my lap. Jamie wasn't exactly a Little Leaguer; he was a member of the Challenger League, a division set aside for kids under 18 who have developmental disabilities.

He had started playing Challenger League in 2002, and over his first two years I'd been struck by how pleasant an experience it was. Jamie has Down's syndrome, and up to that point, he had never played any form of organised sport; his older brother Nick had earned a black belt in tae kwon do and played some junior varsity high school basketball, but had never wanted to play Little League. My career as a young athlete was much more intense: I played youth ice hockey in New York, New England and eastern Canada, and my father logged approximately one trillion miles ferrying me around to practices and tournaments. My children, by contrast, had let me off easy.

Little League baseball in Pennsylvania can be very serious business. Every summer we host the Little League World Series in Williamsport, at a baseball complex that sits at the end of an unassuming residential street in a quiet part of a small town in coal-mining country. (Jamie and I have been there a few times: it is a genuinely weird experience, driving down a tiny side street that somehow opens on to a hidden world where thousands of people are watching - and ESPN is televising - a competition that involves children from around the world.)

And for many years, Little League was notorious for eliciting aggressively bad behaviour among coaches, players and (most of all) stage fathers, who seemed determined to live their sports fantasies vicariously through their children. Youth baseball, I thought, was a world in which parents threatened and assaulted umpires, where coaches threw temper tantrums and water bottles ... and threatened or assaulted umpires.

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In a western Pennsylvania children's league some years ago, one coach actually paid a seven-year-old player $25 to injure an autistic teammate in pre-game warm-ups so that the team would have a better chance of winning. The young hired gun, after striking his teammate in the head and the groin with a ball, eventually told police of the arrangement (after the victim's parents had investigated their child's injuries), and the coach was arraigned on a variety of criminal charges. The league president, Eric Forsythe, a friend of the coach, told the press that the incident had been "blown out of proportion".

All one can say is that these forms of evil are not specific to baseball; parents who get involved in other sports are often worse. Hockey parents have been known to attack one another and to hurl objects at referees; my own hockey dad was mild by those standards, but was capable of advising me never to pass to a rival teammate who was vying with me for the league scoring title. It hardly mattered, however, because my rival's parents had advised him never to pass to me.

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But Challenger League is a world apart. The games are deliberately uncompetitive in every respect: no one keeps score, no one counts balls or strikes, and everyone reaches base. The games last two innings; an innings is over after every child has batted, and after the last batter makes contact with the ball, be the ball fair or foul, everyone rounds the bases for home. Often, after a batter has struck a ball, coaches will throw a few more balls into play so that everyone gets a chance to field. It's like sport without the thrill of victory or the agony of defeat.

So it was especially surprising to me, that April morning, to hear my sweet, mild-mannered Jamie start grousing about how he hadn't been picked to throw out one of the ceremonial first pitches on opening day. Three or four children had been selected to throw out the first pitch from each of what seemed like dozens of leagues, divisions, conferences and associations. So I was grousing about the ceremony of a first pitch that went on for over half an hour, and Jamie was grousing that he wasn't a part of it. I had never even heard him grouse before. But there he was, in his cap and jersey, muttering: "I can do it better than Jake."

"Did you say you can do it better than Jake?" I asked, sotto voce.

"Yes," Jamie insisted. "I should throw the pitch."

"Now, listen," I replied, completely unprepared for this. "That's true, you can throw better than Jake."

This was a strategic concession; there was no use denying it. Jamie has, and always has had, a terrific arm: his throws are accurate and absurdly strong, often too strong.

"But this is not a competition, Jamie. Jake was invited to throw the ball this time. Maybe next year you will be invited. But now it's Jake's turn, and you have to wait your turn."

This mollified him somewhat - but it also produced in him a determination that come April 2005, he would be out there on the mound, ball in hand, all eyes on him.

And that's what happened, one year later: Jamie threw out one of the first pitches, and he did it reasonably well. I posted pictures of his pitch - as well as some of his informal batting practice, with me tossing him underhand pitches in a batting cage - on my blog.

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In response, readers suggested that I should throw overhand to Jamie, on the grounds that overhand pitches are easier to see coming in. I took up the suggestion, and sure enough, before too long Jamie was belting line drives and hitting the ball out of the infield. This was something no other Challenger League player could do, and it established him as the most fearsome slugger in a decidedly non-fearsome league.

Along the way, I taught Jamie a new word. When he and I began travelling together in 2003, partly so that he could see more of the world and partly to give my wife Janet a childcare break for some of my journeys out of town, I taught him a couple of words of praise for good behaviour: he was "observant" (looking out for taxis and finding his way around town), "conscientious" (keeping track of his stuff and doing the right thing without being told) and "patient" (critically important for airline delays, long hire-car queues and assorted aggravation). Now I told him that he was also, much to my surprise, "competitive".

There was, of course, a downside to this new feature of Jamie's psyche, and I triggered it a few months after his historic first pitch when I tried to show him how to improve on his Harry Potter CD-Rom game. Janet and I had bought him the game in the hope that it would improve his hand-eye coordination and give him some purchase on the world inhabited by his brother, the world of Xbox, PlayStation and EA Sports.

Jamie had reached that crucial point in a young intellectually disabled male teenager's development when he was no longer satisfied to be "included" among his older brother's gaming friends by being given an inoperative console and being encouraged to pretend he was really playing along, but was not yet proficient enough to be given a working console and welcomed as a teammate or opponent. So when I noticed that Jamie was having trouble using his computer mouse to trace some of the on-screen patterns that would enable him to use spells such as "Alohomora" and "Wingardium Leviosa", I showed him how to hold the mouse steady, unlock the spells and earn extra bonus points.

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That was a very serious mistake. Once Jamie saw that his scores of 51 and 52 per cent accuracy - just barely good enough to squeak by - could be bested by his father's 84 and 87, he stopped playing Harry Potter computer games altogether.

"Great," Janet kindly observed, "you've ruined it for him."

That phase lasted nearly six months; and when Jamie finally returned to his computer games, I made a point of telling him - quite honestly - where his gaming skills were better than mine. We quickly struck a deal: Jamie would handle all the tasks in Hogwarts and around the grounds, and I would take over for the Quidditch matches, which involved flying tasks Jamie hadn't mastered yet. That was in spring or summer 2006. Four years later, he has become a better flyer and a better Quidditch player than I ever was.

Last year, he entered serious competition for the first time - Special Olympics swimming meets. This was my bright idea for 2009: since Janet and I are always worried about his weight and the health of his heart (although both are fine for now), and since Jamie loves swimming, I thought the meets would be ideal.

I found that some people think of Special Olympics as if it were another version of Challenger League: no agon, no striving, a happy land where everyone gets a medal just for playing. But I also found that Jamie loves a challenge - if it's a real challenge.

In his very first meet in April 2009, he won gold medals in the 25m and 50m freestyle. Then, for the 25m backstroke, the meet officials combined his heat - consisting of three teenagers who had posted qualifying times of about 40-45 seconds - with that of two adult swimmers whose times were 32-33 seconds. Jamie's best time in practice runs had been something like 43.5 seconds.

I filmed the race like a dutiful dad, but I noted with dismay that at the halfway mark, Jamie trailed the field. As he got closer to my end of the pool, my camera angle focused more exclusively on him, so I didn't immediately realise that when he touched up, he did so in first place - for the third time that morning. He had overtaken the other four swimmers in only 12-13m.

Not until later that night, after I had replayed the race a few times on my laptop, did I discover that he had briefly looked around in the middle of the pool and found that he was trailing - whereupon he had reached down and found another gear, churning his arms and legs frantically to beat his personal best time by just over 10 seconds.

In the statewide competition two months later, the best he managed was a silver in the 50m freestyle - but that was all right with him, because he shaved another couple of seconds off his personal best in the event. Citius, altius, fortius, you know the drill.

So it turns out that I have an 18-year-old with Down's syndrome who has a fierce competitive streak. Who knew? Even Jamie himself was unaware of it until he entered adolescence. It feeds his sense of self-esteem, it helps to keep him in shape and it affords him some pride in his accomplishments.

But how is one to walk that line - whether one is disabled or hyperabled - between legitimate pride and obnoxious, overweening hubris? Between a sincere desire to improve oneself and a brittle, bitter determination to defeat other people? The other day after track-and-field, after Jamie spent some minutes enumerating all the people he had beaten, I had to remind him that although he runs well, he is not the fastest runner in his group, and that the real challenge lies in learning how to be competitive while being gracious when you run up against a better athlete.

And then there is the Father Factor: what is the difference, for me, between helping Jamie along, offering him love and consolation and encouragement, and being a crazed sports parent who instils in one's child a maniacal desire to outperform others - and a concomitant fear of failure?

I think I have finally reached a stable equilibrium with Nick, now 24: he understands that I will deal him heartbreaking losses in ping-pong and I understand that when we play darts he will wipe the floor with me. We will simply respect each other's talents in these critical indoor sports.

But I never expected to confront this question with Jamie, although I should have known better. After all, I've long since grown immune to most of the cliches about children with Down's syndrome. Jamie is not an angel sent to humanise the rest of us; not a sweet little dollop of smiles and passivity. He is an ordinary human being, full of passions and desires that are at once admirable, dangerous, contradictory and utopian. It is a lesson I have to relearn at every stage of his life, it seems. I can only hope that I'll get better at learning it.

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