probably when you're downloading apps or content from store, the age restriction will limit stuff
Yeah, I'd imagine. I bet you could switch the age on an account, install what you want, and then switch it back to <14 though.
There could be other issues though, like Edge filtering searches, etc.
I sort of thought the MS Family interface would give me a harder time, since it was pretty obvious that I was trying to "cheat" a bit.
Having Cortana turned off for <14 seems odd anyway, and it's particularly irritating, since Quiet Hours are buried in there, a very handy feature for students...