It is best to start the process of looking at schools about four years prior to entry. Most schools have a cut-off date by which your child must be registered. Some schools will take registration only up to a limited number, with names being placed on a waiting list if normal lists are full. There may be some places reserved for strong late applicants. In the UK, preparatory schools tend to not have absolute cut-off dates while senior schools have dates that vary widely from three years prior to one year prior. For entry at 16+ years old, registration is usually required at least one year prior. However, schools have taken in students in special circumstances at short notice. As a general rule of thumb, the earlier you start the process, the better your options and wider your choices.