No way I would ever have more than 3 kids in a house. Sim kids are just too annoying. You have to teach them all that stuff which takes an eternity or they don't grow up well, when they get to school age they spend hours going to school and doing homework but they don't learn anything (skill wise) so you still have to have them learn skills too. If you are not careful you get a visit from a social worker so it is all risks and no rewards.
It would not bother me to have them if they learned some skills in school that made it easier down the road but school is the big black hole of time where nothing positive happens for the house or the sim and you are not able to do anything with them.
Having sims learn skills is boring. Anyone ever try to master cooking just by cooking all the meals? In a normal life span it never happens. So you are forced to have them read books. I'd rather read a book myself then sit and watch a computer character read.