Why don't schools in the Sims have actual grades, instead of just elementary school and high school?

Probably cuz there's no gradual aging. It's not really necessary if all the kids are the same age as all other kids and all teens the same age as all other teens. We're really missing a lot of life stages in Sims 4. It's still my fav game of all time, but I'd love to see a difference between a 13 and a 17 year old, a 2 year old and a 4 year old etc.