> 2. Within a given year, older kids are stronger, faster, etc., and perform better
I've seen a few youth ice hockey games and by god it's just unfair; there's a kid like a foot taller than the rest. I'm kind of surprised there isn't some system that buckets kids by size , it can't be fun for the small kids to get elbowed in the neck every time they bump the tall guy.
Fun fact, the ball and hoop don't care about any of that. It lets me steal it from you and it lets me put it into the hoop. The scorekeepers even add two to the scoreboard!
Tangent: I grew up around a high school basketball coach and saw that all of the adults knew exactly who was going to college in which sport, and usually by late jr. high. We'd go to games just because he said some kid on the visiting team was going pro and that's exactly what happened.
My kid is in 12U youth hockey and is a big guy, and yeah, smaller kids can often usually skate around him, but if they bump into him, they fall over, and often he'll get a "big kid penalty" which means he gets a break in the penalty box for the crime of being tall and physically near a smaller player who fell over. We had to do a bit of coaching on how to make (allowed) physical contact so it reasonable contact doesn't look like prohibited contact (mostly be sure to have hands off when kids are falling, it's real easy to look like cross checking when it was actually just incidental contact).
Some of the littler kids seem to have a lot of fun getting away with a lot more physical play than he can. Although he says he enjoys it when a small kid gets mad at him and tries to knock him over, too. So at least so far, seems like everyone is having fun.
I don't think you can really just bucket kids by size and ignore age though... there's a lot of mental development between 10U hockey and 12U hockey, and putting a big 10 year old on the 12U team is often not right because the level of play is so much different, most 10 year olds won't keep up. At the same time, a small 12 year old on the 10U team is going to have a big advantage from age.
Around here we do have two different leagues, one for 'recreational' teams and one for 'reputation' teams, and you more or less have to demonstrate a decent amount of skill to get on the rep team, and then you're playing with much better teams. All the teams are composed of a mix of big and small kids though.
Edit to add: All that said, I think bucketing kids by age makes sense and I agree that there can be advantage to being at the extremes of the cohort. Since the US school system usually has a different cutoff date (september-ish) than US youth hockey (jan 1), you might see different results where there's grade level based high school hockey and age based youth hockey... but not in Canada where the cutoff is Jan 1 for both.
The problem is that these youth sports can get very competitive, and then people will be tempted to move the bigger kids down to get an advantage.
USA Hockey rules don't permit playing down unless a doctor says it's medically necessary, but then they're not allowed to play on competitive teams. Simply being small or unskilled is specifically not an acceptable reason. [1]
IMHO: playing up is pretty easy to administer, but playing down would be very hard to administer fairly for competitive teams, so it's just flat out prohibited.
Edit for further thought: If you have enough participants, it might make sense to try running Jan 1 leagues and Jul 1 leagues and see if it makes sense to go to quarterly leagues too. Or maybe agitate to change the cutoff for Spring Hockey and see how that looks?
[1] https://www.sedistrict.org/page/show/834907-playing-up-down
A friend of mine has a son who is giant for his age. The kid is 7 but he's the size of a late middle-schooler.
One of the things that ends up being really difficult for him is that everyone around him assumes that he should be smarter and more mature than he is. They inadvertently expect him to be mentally the same age as kids the same size as him. It sucks because it makes him seem developmentally disabled or emotionally unregulated. He's not! He's a totally normal seven-year-old. Just a really tall one.