I wouldn't say 80 hour weeks are the norm if you are in a normal school. 60 hours yes... 80 hours usually only happens during test/exam weeks, or term 3 when all the **** hits the fan.

But yes I have heard that some schools are hit hard by resignations and are surviving on FAJTs. If MOE is not careful, there may be a cascading effect as more and more teachers will resign in these schools due to excessive workloads from lack of teachers.