Sounds to me you are doing more then needed already.
Coubld be a possible mod conflict or your lot got corrupted somehow. Did you check to make sure all your mods are up to date?
Which EP's do you have?
I've been able to put teens and kids to private school with AL without any problems and I did not go into as much trouble as you.
Is this happening only on this specific lot or on all your lots?
I have all EPs, I'm not sure about mod conflict though, I don't have too many loaded. I'll try to see if it's just this lot or all lots.