Secondary school, 4 levels, American English The series that helps students to appreciate the world outside the classroom. Crossover Intro & Plus promote the acceptance of all cultures, socioeconomic situations, ages, races, opinions, and beliefs. A respect for life, dignity, and the rights of others are also key themes, as well as a focus on modern-day global issues such as the environment and technology. Crossover provides a solid foundation for language development, with plenty of opportunities for teenage learners to express their opinions.