A supply teacher essentially has the same responsibilities of a permanent teacher but they may not have to undertake all of the same tasks every time. For example, if a supply teacher is coving a member of staff that is off ill, then the lesson may of already been planned for them and worksheets created etc. Supply teachers are still responsible for marking pupils work and giving them feedback and all lessons must be taught in accordance with the National Curriculum.
As a supply teacher you may even have to take children out on field trips or assist with monitoring work placements. If you are covering as a supply teacher during exam periods then you may be required to participate in the exam set up and also overseeing the actual exam taking place.
You may like the challenge of going in to a classroom without having had time to read through or create lesson plans or this may worry you a little. If you are a supply teacher then it is always a good idea to have a few lessons up your sleeve that you can turn to should you be called in to a situation last minute where there is no lesson pre planned for you to use.