After-Effects class for 15-year-old in Massachusetts?

When someone wants to learn Visual Effects or Animation production the software is a very small part of the equation. Make sure you vet the trainers you pick. It used to be that most folks using AE were pretty competent filmmakers and most of them did it for a living. Now the AE user base is so full of amateurs and enthusiasts that it is very easy tutorials and even trainers that are not going to give you good information.

I would check community colleges in your area and contact high schools. When you find someplace that teaches an After Effects class make sure you check their resume so they don't waste your son's time and fill his head with ineffective techniques and unrealistic information.

For just learning how to use the software Lynda.com is a great resource and the After Effects product page is a great place to start. Adobe has created a great point of entry and you'll find it here: Getting Started.

If your son is primarily interested in animation I would start by buying a couple of books. If it's visual effects then I would also start with a couple of books. The techniques of planning and executing a project are not specific to any software, and if you only learn the software then you'll have a very hard time doing anything but following tutorials and imitating someone else's work. 

Here are some good books: The Filmmaker's Guide to Visual Effects: The Art and Techniques of VFX,  The Visual Effects Producer: Understanding the Art and Business of VFX,  Masters of FX: Behind the Scenes with Geniuses of Visual and Special Effects.

For animators: The Illusion of Life: Disney Animation.  Directing the Story: Professional Storytelling and Storyboarding Techniques for Live Action and Animation.

Actually, everyone that wants to make films should own a copy of The Illusion of life. You son should also study, and by that, I mean read, everything he can find on Art, from the grand masters to the impressionists, lighting for photography, the art of telling stories, classic literature, and human behavior. Without a really good background in all of that the only jobs available are those of technicians and they don't get paid very well. With a good background in everything that makes human beings exceptional, your son would have a chance to make a huge difference in the world because there is no more powerful way to tell a story than with pictures and sound.

I Second bob's suggestion on Lynda. Great training structure for a lot of apps and in an affordable price. for classroom training I would look also here: Adobe Partner Finder | Adobe Training & Certification

You might want to download the trial of Lynda.com and see if that will work for him:

Online Video Tutorials at lynda.com • lynda.com