There’s some great perspectives on self management in children here: What is the RIGHT age (self-management)
When I was in school, diabetes management was different than now because of cgm developments. I had I would say minimal nurse involvement. I would go once a day before lunch to test my blood sugar, and I believe she helped me calculate how much insulin to give myself certain days. Though most days my parents left a note in my lunchbox with how many carbs to put into my pump when I got one (before when I was MDI I think we just did a lot of guesswork). At a certain point I just used the nurse’s station to hold all my diabetes supplies and managed my care on my own (not sure on the age range when this happened).
A girl I babysat for had a phone connected to her cgm. Her mom followed her cgm data and would text her with diabetes things to do throughout the day. That seemed to work pretty well for them, and I think some parents here use a similar system that I’m sure they can talk more on?