For most people who have been out of education for a while, a few days of maths revision prior to starting ATPL study is extremely useful. Most schools provide a maths test prior to signing-up for training. This should help to identify any problems.
Some schools also provide a short maths revision course at no extra cost as a lead-in to the first module of study. If your school offers it, you should take full advantage of it. If you are considering going to a school that does not offer it, then you should ask them why not. It costs them next to nothing and is invaluable to instructors and students alike.