"Compulsory schooling" refers to a system where children are required by law to attend school for a certain period of time. It means that going to school is not optional but mandatory for all children. Full definition
What head teacher could ignore a letter from a parent saying that they do not wish their child to participate in this test when that child is not even of compulsory school starting age? (neu.org.uk)
They refuse to determine which year group it is in my son's best interests to be placed when he begins school at compulsory school age. (schoolsweek.co.uk)
By state law he is exempt from compulsory school attendance this year. (firstthings.com)