Yeah, I have tried unsuccessfully to add schools to that as well. That site is frequently down, and doesn't seem to work so well. A bunch of schools just don't show up when I've tried to add them.
When you are adding schools are you just clicking on the plus next to the name?
If you are not entering a date for the Primary or any other category it won't show up.
As far as I can tell clicking the plus is just expanding the menu and not adding the school.
Bear in mind I have nothing to do with MDapps, this is just what I have found while messing around with my personal MDapps after becoming aware of the issue.
Just wanted to say that the person in charge of MDapps posted the yearly thread in Pre-Allo asking for suggestions/feedback. If you have anything to add, now's the time!