Our endo has flat out said he doesn't want to see our kids below 6.7. The ability to feel lows is a function of deviation from the norm and that when kid get A1C much lower they don't feel lows as much or at all.
He keeps telling us about one patient (fictitious for all I know) who's parents obsess with low A1C. The doc says the kid is in a constant state of hypo and the parents will not listen to his advising higher targets.
We usually don't get to the 6.7 anyway. The kids are growing like weeds. Growth takes energy, energy is carbs, carbs need insulin, by the growth comes in spikes and keeping balance is tough.
Teens need rational parents to cope with their relative lack of teen rationality. One thing to be rational about is not making diabetes care a symbol of parental control. If parents obsess about A1Cs the kids may rebel against the diabetes care not the parents and you want them to rebel so they move out after college. You also want them to be self sufficient in their diabetes care when the move out.