The break needs to be roughly in the middle of your work time, with emphasis on "roughly", you need to show some flexibility.
Say you usually work 8:00-17:15 with 45min break from 12:00-12:45 but today there's a meeting from 12:00-13:00. In such a setup you can be expected to take the break either before or after the meeting, the employer OTOH must provide the opportunity to do so.
They're probably exempt. Zürich's Lehrpersonalverordnung for instance says the trial period is five months even though the Code of Obligations says the maximum is three months - assuming the former would hold up in court, certainly the teachers association (LCH) would intervene otherwise.
I don't know the sort of annual leaves that are available to teachers here in CH (are we talking primary, secondary, tertiary?).
In defense of teachers at university level, all "leaves" are used for conference travels, and yes, then people try to squeeze a bit of family vacation time in there wherever possible - that usually means that the professor spouse has one schedule, and spouse (plus kids if any) a separate one. That's some "family" vacation I don't miss.
Meetings or seminars during lunch is a bad habit, it happens a lot at university level (well, at least the ones I know of), and hope it doesn't become de rigueur. Worse is when (crap) lunch is provided.
That's not how it works. If the total time spent at work is 9 hours or more, the employee must take a break (or breaks) totalling at least one hour, which means that if s/he is at work for 9.25 hours (as in your example), s/he will be paid for 8.25 hours.
You forgot the usual "and it is not real work but just having fun with kids " comments.
I think the "emergency" meetings when it revolves around some kind of urgent case management can be called up anytime because we have to be available for non-teaching admin time, to my experience. But it shouldn't interfere with the law that insists on breaks. One thing is, it is really difficult to get all people present so lunch time is often the safest bet. Bordeaux or not.
Lunch is probably THE most individual thing in Switzerland.
I experienced everything from "I dont do lunch" over sandwiches, microwave food, take away food, proper lunch food, buffet lunch up to fine dining lunch in my career. Laws are clear, personally never found them enforced though.
Switzerland is kind of weird. Take the workweek in the first place, one get a contract for 41,5 h a week, who and how could account that? Why not declare a round 8h day workweek as the rest of the world (mostly I guess...).