Many high schools and middle schools across the country have zero period classes that meet before the start of the regular school day. Classes offered during zero period usually fall into three categories: 1. Elective extracurricular classes (e.g. music: art); 2. Advanced academic subjects (e.g. IB History; Physics); 3. Remedial classes. Zero period classes are often oversubscribe as they are sometimes the only period that some classes are offered.