I believe Yale set up residential college system based on Oxford. So far, Yale has 12 residential colleges and plan to build two more. If Yale has 1300 undergraduate students, then each residential college has about 100 students from each of 3 or 4 grades. The total is about 400-500. Most freshmen live together on old campus. Freshmen are randomly assigned to a specific college unless you are a legacy then you can choose to or not to go to a specific college. Each residential college has a college mater, a dean and some student counselors. There are some faculties members live in the residential college with their families.
The reason Yale wants to do this is because Yale becomes larger and Yale wants students to have a small college feel. Yale is well-known for the best residential college system in the country. You can go to school website for more details.
