I know a Maths teacher who only ever gets day to day supply teaching in any subject but his own. He meets design technology teachers/cover supervisors and P.E teachers all teaching maths lessons but never actually gets to teach it himself! Supply co-ordinators in secondary schools really need to "co-ordinate" their lessons to match with a teachers specialism. It might be difficult but surely it is a massive waste of money and time if a Maths teacher is covering lessons in say French or Geography when in the exact same school, Maths classes are being taken by non-specialists! If I were the parent of a child having lessons in this way I would be very upset!