In that price range you will not get a laptop that will play the latest games, you will however find plenty that will be OK for coursework and for surfing the net.
Check with your son the importance of portability as some of the larger screen machines are heavy and more suitable for replacement desktop use. There are some laptops that are small, with long battery life and great to use on the move.
Personally I like Toshiba and this website click here will allow you to put in various parameters to guide you on the most suitable laptop from the Toshiba range.
Once you have got your new laptop the free Open Office package click here is seen by many as a good alternative for coursework rather than the more expensive Microsoft Office.