As a coordinator of a High School, I developed a project to place students in different classes according to their achievement in English, skills for the language, commitment to study and so on (e.g: a student may be in level B in the English class, regardless if he is attending 1st or 2nd year at the school)The results have been really positive. The point is that some of the school authorities are not really convinced and are asking me fot the theoretical framework to support the project. I made the project based on both my personal experience and the experience in other institutions.

Any ideas where I can find this theory to back up this project?

Thanks for your help.