As Steve says, only the magic lantern 3rd party firmware offers Canon anything dramatically better in terms of video. They're both in the same ball park really, and as bad a Pentax is at video, it's all pretty similar at that age/level.
Video camera alternatives in that price range, such as Handicams, don't offer a lot of actual cinematography features. Continuous autofocus is nice, but it's prone to hunting if poorly implemented. There are basically no depth of field options, as typically everything is in focus. In short they are great for holidays, but aren't that stunning if you're trying to teach basics such as shot design, stabilised or fixed mounted cameras, lighting, sound, composition etc.
Fundamentally where Pentax falls down is in it's lack of aids to the user during video capture. There is no mechanical stabilisation, no 'zebras' to warn for over exposure, no focus peaking during recording etc. Pentax is pretty well equipped with frame rates and full manual control if needs be. Given there is not much wiggle room to adjust the image in post afterwards, getting the correct exposure is critical.
Pentax for photography is significantly better than the canon equivalent in my experience. The K-mount does offer heaps of cheap manual focus lenses, and the digital zoom and focus peaking works really well for tripod based narrow depth of field shots etc.
The flip side is that Pentax is not as common as Canikon, so students are far more likely to use Canikon in the big wide world afterwards. The use of say a Sony NEX system camera could allow for wifi to tablets or cellphones, to view the affect of depth of field aperture changes in real time etc, which may be useful for teaching. Alternatively using the HDMI out to a projector or large TV could be done on a Pentax. Teaching wise there are lots of options.
For the budget, I don't think anything in the region is going to be dramatically better or worse than anything else. Perhaps better at one or the other, stills or video, but not overall at both. Pick something, relax and teach