You can install multiple versions of Sonar as long as
you are the only one using it.
Here is the policy on educational use.
http://www.cakewalk.com/Education/Eligibility Even though I have the full version I bought HS because the price was right for what I needed it for.
It is pretty much the same as the main versions without the fluff.
It would certainly be perfect for teaching as it is simple and uncluttered.
It's biggest weakness is the SI drums which are IMHO, useless. I am going to put in a plea that they at least have a few options on the sounds. TTS_1 sounds better to me and that's not saying much.