I have converted my building into a school but now I can not convert the building to anything else even though it says "this villager thinks this building can be converted." Is there anything I am missing? I have tried placing my master scientist and master builder on the building but nothing happens. Please help. thanks.

There isn't any additional conversion possible. There are many discussions of that issue in this forum, including one here if you'd like to read more.

no, you can't convert it any further.
i hope i helped

I've been wondering about the school, what exactly does it do? I don't see any differences in the kids' stats when they go to school at the drumbeat (that small drum on the right)...

The school helps the kids when they are born (with additional skill). Banging the drum only calls them to get them in one place.

thanks! i've been beating the drum like crazy thinking they would accumulate skills later on lol! after all, none of my village kids have fully grown yet (not in the "school generation" that is ;))