Looking at the comments below has me realizing that apparently most people have never heard of a Student TA before which, in my opinion, was pretty obvious that's what Cheerilee is more than likely meant to be in this universe. Did no one else have student TAs in their highschool before???
Anyways, this is a VERY cute pic~ X3 All of your art is very cute to be honest.
Okay. Here's a cannon. It may be a bit bad, with the logic though. What if Big Mac stays back every once in a while, and he makes up all the work he missed. And what if Cheerilee was just a bit young, and she excelled in her education, to pass onto teaching at a young age? I know it sounds a bit off, but that's the best I have.
the human world isn´t so like Equestria, They could be the same age as ponies and I love that ship with all my heart but, as humans, it´s just the awkward, tipical and so seen "teacher so nice and pretty that male student wants her but she´s oblviously not interested cause if she were it will be creepy"
There actually was a scene of him with the student body and he wasn't dressed like a teacher or faculty member, giving no visible proof that he was with the faculty or that he wasn't, as opposed to Cheerilee who was visibly one of the faculty members int he library. Until I can get more proof, though, I'll let it go here.
I wouldn't pay attention to what the movie says about their ages. I mean, the CMC are in Highschool. Highschool! That pretty much throws the whole age thing out the window. (Also awesome picture. Love Scootaloo's expression)