I agree with MissMillicent (sp?) the production team will have a story arc - teacher struggling, class out of control, triumphs in the end, kids on his side, and then the film will be edited accordingly. I thought they had cameras rigged up in the school as they couldn't really have a camera crew trailing around the school. I was surprised though that the filming was only for half a term; I would have thought they'd have filmed for a lot longer.
I know a family whose children are on a TV programme "Child of our Time" and they film for about 12 hours in the house and then the children are maybe shown for 3 or 4 minutes at most! Don't know if anyone saw the Channel 4 much talked about "Benefit Street" as apparently they filmed for 12 months for that programme of around 6 episodes I think.
I think these programmes could become very formulaic. There was some programmes on a while ago about the Teach First teachers who were placed in secondary schools with poor catchment areas, and it was very similar. One particular young Asian woman was seen to be totally out of control with the kids running rings around her and then surprise surprise it all came good in the end.