First off, I would say make sure your availability is correct so you don't get scheduled when you aren't available in the future. I assume this wasn't a last minute surprise class that just popped up, and waiting until the last minute it seems to deal with that fact. By waiting until now to deal with it, you aren't really being fair to anyone you work with.

Secondly, if you need to call out in the future, food poisoning is the way to go. Very simple symptoms to say you have and you legally cannot come in to a food service environment with vomiting and diarrhea.

So the standard for calling in sick has always been 3 hours minimum and if you're sick you don't need to find coverage.

However- was your class a last minute class? I don't know how things work in other countries or schools of course but when I was in uni then the classes were set and any exams etc I had 2-3 weeks notice. That way I could book it off or change My availability.

If your manager scheduled outside your availability- that's on them to find coverage. If it was within your availability, it's unfortunately on you to find the coverage.

If you had notice- the class date had been known for a while and the schedule was out the standard 2-3 weeks prior, then sadly it's your responsibility to find coverage for that.

Either way if its your first incident then you will just get a write up- no big deal.

You’re supposed to be allowed to call out as long as you don’t miss more than 25% of your shifts. You’re not supposed to find your own coverage if you’re sick.