I don't like to see kids cry from stretching, that seems like they are stretching too far. But conditioning? My son has cried a few times this summer while doing summer conditioning. I have talked to him about it and decided I'm OK with it. His coach has even commented in it - my son and a few other boys keep going with conditioning even when it really hurts, they cry; but keep going. Some of the other boys don't cry; but you see them stopping before they hit that limit. So sure, my kid is crying; but he is choosing to keep pushing himself rather than taking a break. I have used it for inspiration for myself in my own workouts. I feel like I can't possibly do one more of whatever exercise and I want to stop, then I think about DS and realize I'm not even near crying, so I suck it up and keep going to finish the set. Even still, I realize I have never worked as hard in a workout as he has.
DS's coaches rarely fuss at the kids who stop for rests if they think that the kid really is near their limit; but at the same time the coaches have taken notice of DS and the boys who push through and don't rest. I have talked to DS even right after practice and he says he is fine and it never makes him waiver in wanting to go to practice. Though, DS is 11. I'd likely feel different if he was 7.