When I was doing Yr 12, I would occasionally miss some of school, due to fire calls...usually when it was an early morning call, I went, and then ended up late for school - my school were happy with the arrangement, as were my parents.
I generally didn't leave school in the middle of the day, as the appliance had already gone long before I could get there, but I did miss a bit of school here & there.
When I went to Uni, I did CFS, and took on Ambulance duties as well - (nothing like doing an 1800-0600 shift on a Sunday night, and then turning up to Uni for 8 lectures in a row the next morning!) I only missed a few lectures due to Ambulance, and CFS duties.
Oh yeah, I passed both Yr 12, and completed my degree!!
As for whether or not people should leave School / Uni to attend CFS calls, one thing I find in my paid job, is how naive many of the kids now days are, in relation to what happens out in the real world.... leaving school / uni on an occasional basis might actually be good, as it exposes some of these kids to the "outside world" - as long as it doesn't happen all the time, and the School / Uni work doesn't suffer, what is wrong with it?
And these days, the trend is towards kids being exposed to a bit more of the real world, before being launched from school.....so being part of the CFS, and having an opportunity to be part of something that allows kids to develop skills, mature, learn to take some responsibility, and be good for the community, can't be a bad thing in my books!
Pip