Although it's possible for someone with type 1 to have an A1C below 6%, it's very difficult. I've known a few people like that, and they are all super users. It's also going to depend somewhat on the lab running the A1C test, personal biology (A1c is not only affected by blood glucose levels) etc. 6-6.5% is superb control! Parent should be very proud. 6.5-7% is still very good, I haven't looked at the distribution of A1c's for T1D recently, but that would be much better than median which I think is above 8%.

Especially with kids, it's difficult since you don't control how much they decide to eat making pre-bolusing meals challenging (part of why reducing carbs tends to be helpful for people is it reduces the need to pre-bolus and makes it less risky since you need less up front meal insulin).

I didn't mean to say it's not superb control for someone with T1D, only that there are likely still some negative health consequences at 6-7%, and that exercise after carbohydrates is one mechanism of potentially getting some additional marginal improvement.