Yes, every student has the right to change school. There could be many different reasons for this, for example due to moving house, not liking the school, having conflicts within the school, etc. These are all understandable reasons, and no detailed explanation of it can be required from the family.
In case a student decides to change school, the student together with a parent/legal guardian should contact the new school and inform the current one. If the student is applying to the school that is the one obliged to provide enrolment, the school must enrol the child. In all other cases, the school director can decide on the enrolment and set the entry criteria. If the new school accepts the enrolment request of the student, the student has the obligation to withdraw from the other school.