Well this may put things in perspective.
I was an Aeronautical Engineering Student at a school that required ALL students to purchase a laptop. and even though all the professors knew the student had to have a laptop they never made assignments dependent on having it in class, since often enough there's multitudes of students having issues with their laptops and would be unfair to have any graded assignment dependent on having your laptop in class with you. That being said there were a couple mostly advances computer science classes, CAD, engineering design classes that would be very very difficult without bring the computer to class or labs.
there were students who had larger screens there's no problem with that but its slightly inconvenient in terms of portability, so that would be up to your son. Acer is a good company, personally I would stay away from Dell, Have never been a fan of their support or hardware. Mac would also be a slight hindrance in terms of compatibility (less so as time goes on) If it were me I would look for a 15" screen, with an i7 processor, 7200RPM HD, Keep in mind if you get something good now it should last the 4 years, but something too cheap will get too outdated and need to be updates in 2 years or so. Luckily with laptops it is possible to get state of the art hardware in the $800-1200 range.