The Razer Blade Stealth is a great option, in my opinion. It gives you an ultrabook form factor (12.5 inch screen, 2.75lb weight, half inch thickness) with a pretty great amount of processing power, not to mention the ability to hook up to an external graphics processing unit (GPU) while at a desk to achieve desktop-levels of computational capability. (good for graming) If your son is happy with his current gaming rig and simply wants a device for academic use, a Surface Pro 4 with a Type Cover (keyboard case) is a great option. It is primarily at tablet, but can be used as a laptop would with the addition of said case. The price for these two systems is about the same at $999 by the time you include the cost of a case for the Surface. It’s really all about what you want. There are many different options in the thin and light category of computers.
In my opinion, have your son wait until a month or so into school to see how he uses a computer. By this, I mean does he find himself studying in his dorm or the library, taking his laptop everywhere or just to class. When I got to school I had a 4 year old MacBook Air. I knew I would need to upgrade, but I wanted to see what my needs were first hand. Now, I have an iMac that I use for 90% of my work, and take an iPad with me to class since all I need to do on the go is take notes, type emails/messages, and read. If your son is an avid gamer, he should know quite a bit about computer specs and different models, so ultimately he should decide what he’s comfortable with.