If you are absent from school without an explanation from your parents or carers, the school will make enquiries as to your whereabouts.
You may also get a letter from the local education authority (LEA) and/or a visit from an Education Welfare Officer. An Education Welfare Officer is responsible for checking on students who don't turn up at school on a regular basis. They will investigate your problem and help to try to resolve it, often with advice from teachers and parents or carers.
Bristol's school attendance website