I have two issues

You could have too many children, as TadOlson mentioned, so some are randomly excluded. However, you don't NEED a mod to fix the issue. If you have too many school-aged kids, you can simply place another school on an empty lot. Then enroll your kids in that school. Having NRaas mods will help as you can assign other kids in the neighborhood to the school you wish them to attend. Eventually, kids would start attending the closest school; but those already enrolled in the old school would continue there without redirection.

I love creating a caste system for the schools so that one is an elementary school and the other is a high school. This means that they can meet all the others their same age.

With the babies, Sims usually pick them up when they cry that they need attention for a bottle or diaper change, right? (I usually immediately buy a birthday cake for babies after the initial round of interactions.)