All 650 students at Cardinal Spellman High School are using iPads this school year. The college preparatory school in Brockton trained teachers in December, and students received their computers in August at an “iPad boot camp,” according to Nate Merritt, the school’s media coordinator. The iPads are loaded with electronic textbooks, so students are toting lighter backpacks, and the school hopes to move entirely to electronic books in the future. Students pay a $150 annual technology fee and will receive new iPads their senior year.