They aren't standard working terms because of the unions. They are standard working terms because all teachers (who work in state schools at least) are employed by the local education authorities, who in turn set their working terms and salaries based on the government's department for education. So for teachers there is no individual salary negotiation, it's all decided centrally by the government and you either take it, or move to the private schools of which there are a lot less. (This is UK for me, but based on what op said, I think it's similar)