With Highschool pack bringing prom and they being able to date I think current teens are more like 16-19 in age, and with the Growing together making child sims loose their teeth, that happens around the the age of 6, I think there could be another life stage in between child and teen, spanning between maybe 10 to 15. They would be shorter, change their molar teeth, not be able to date, you don't need to hire a nanny for them, they still play occasionally but prefer outdoor games with their friends, basically they would be a mix of both child and teen life stages.