Will your child be changing schools on September 2019? In that case, you will need to register your child again. To do so, follow the registration procedure. Sometimes, you may have priority.
Will your child be changing schools during the school year? Then contact the new school. If the school has any places left, your child will be registered. If the school does not have any places available, ask for a "place application unsuccessful" document. Your child's name will be put on the waiting list then. During this period, your child does not enjoy any priority.