Despite what people may think teachers do have a lot of work they need to fit in, not only during the school opening hours but also afterwards and weekends. It is vital that you have good time management skills otherwise you will struggle to fit everything in and may find that the job becomes extremely stressful.
Planning is very important; you need to know what you have get done within the term and how this should be split throughout the weeks and days. You may also have to plan in time for presenting an assembly to the other classes, report writing, parents evening and possibly helping with afterschool classes.
As a rule, most teachers will do their marketing in the evening and at weekends. Although they are given PPA (planning, preparation and assessment) time, this is usually a few hours within the week and not nearly enough needed for all the planning and marking.
If you are struggling to fit in all the work you need to do, then it is advisable to seek the help of other teachers or speak to the head teacher. They will be able to help you prioritise your workload and delegate other work if possible, to a TA or another teacher.