You could look at an actual implementation of such a system in Germany. They have a three tier structure and divide students on the basis of their "ability" at

You could look at an actual implementation of such a system in Germany. They have a three tier structure and divide students on the basis of their "ability" at a very tender young age of 10 or so ( 4-5th grade). http://www.economist.com/node/5465005 http://www.economist.com/node/5465005