Very uncool of them...and criminal.
I've been "dosed" with acid (lsd) once, and I had a drink spiked with a roofie another time in Vegas while at Comdex back in the day (I think I was served a drink intended for someone else), so I can tell you firsthand that it is quite an unpleasant exxperience.
I consume cannabis edibles on a regular basis and I am sure that to the uninitiated and unsuspecting it can be quite unnerving. I find it easy to work at a highly productive level with a nice body/mind buzz for hours that the edibles which I eat produce, but I know what I'm eating, and at what dosage ("you only need to eat one", as the saying goes
).
I like to do the opposite sometimes...I tell people that regular brownies contain cannabis when they don't. Be sure to give them coffee or cocoa along with it (a warm mild caffiene stimulant), and many people will swear that they are starting to feel the effects after awhile.
BTW: It's good to have some stash to share with them after pulling your little prank though. No harm, no foul.
As for punishment, yes, I would say that the two that served pot brownies to their unsuspecting professor and fellow students deserve some sort of punishment.
However, I think that they know they fucked up big time, so an apology, expulsion, a fine, community service, and maybe even a little time in the clink, but to me 80 years sounds just a tad excessive for a stupid prank.
ADG