If anything breaks, the gears won't primarily be the problem.
Do I have to worry about breaking any gears due to excessive torque?
Do I have to worry about gears slipping (skipping teeth) due to high torque?
I have seen gears get to nearly twenty N.cm without issue, other than slipping along the axle, (easily fixed with bushings), or skipping, (easily fixed by super-gluing your chassis pieces together.)
However! Not all gears are made equal, and I have broken a couple of (gear) teeth in my day. Your 40-tooth gears might be in for a rude awakening as to their structural integrity under high torque.
This can be easily solved, I think, by changing the gear ratios, which will be a great lesson for your students, how big gears driving small ones can make things more efficient.
The "real problem" will most likely be the bricks. Bricks don't stand up to torque as well. If you compress a brick too far, it will snap, despite how tough they normally are, or at least chip.
This may be a hard issue to solve, not to mention the other "real problem" of the binding power of bricks to each other. Fortunately, there is a solution! You just may not like the fix.
Superglue is tough. It stand up to a lot of pressure. As I said in the first bit, super-gluing your chassis-pieces together may be the only way to handle a challenge like this, if your students have trouble with structure.
So say you don't like ruining your pieces' chance of use ever again, like me. I suggest that you look up good ways to structure a Technic chassis, and if a build is iffy, tell them what needs to be fixed.
But for argument's sake, I have tried many things like this, and everything was fine. Just make sure that somehow, every piece stays in place.
But only if you're using LEGOs for the chassis at all!