I have changed from temporary visitor to my current work visa. Changing is possible, BUT it is an entirely different process from the COE route. That means different sets of forms, different requirements (COE not required but helpful) and different timeline.
Obviously immigration does not like handling such cases at all. However it is much easier and accessible than it was before (or so I've heard).
If possible, you will want someone from the school to go with you so you don't end up saying anything you shouldn't.
The wait for the COE can be a PITA. And the wait for approval of your status change is going to feel like another long wait. Just be prepared.
Also, be prepared to do some talking and whatever if you intend to come in with a one-way ticket as a temporary visitor. I heard US citizens have no such issue though.
All the best to you anyways.