Over the past few decades, schools in the USA have been testing various arrangements which break from the one-teacher, one-class model. Multi-age programs, where children in different grades (., Kindergarten through to second grade ) share the same classroom and teachers, is one increasingly popular alternative to traditional elementary instruction. Another alternative is that children might have a main class and go to another teacher's room for one subject, such as science, while the science teacher's main class will go to the other teacher's room for another subject, such as social studies. This could be called a two-teacher, or a rotation. It is similar to the concept of teams in junior high school . Another method is to have the children have one set of classroom teachers in the first half of the year, and a different set of classroom teachers in the second half of the year.