There are different ways to use instructional menus in the classroom. In order to decide how to implement each menu, the following should be considered: how much prior knowledge of the topic being taught the students have before the unit or lesson begins, how much information is readily available for students to obtain on their own, and how self-reliant the students are when it comes to obtaining information. Menus can be used to serve this purpose; whether a student tests out of the entire unit or just one aspect, activities can be selected and offered to replace the standard instruction. The teacher would pick and choose which aspects of the content must be directly taught to the students and which could be appropriately learned and reinforced through product menus. Centers have many different functions in the classroom—most importantly, reinforcing the instruction that has taken place.