It would be slightly more open than a standard beginner moutpiece but still fairly closed. If your son is going to be playing in concert band a link may not be the best choice. It is pretty much a jazz moutpiece. For learning a good student mouthpiece would be more than adequate, cheaper and probably easier to learn on. I'm not an expert on beginner pieces but friends who teach beginners seem to like the yamaha 4c.

For a beginner, I see nothing wrong with a hard rubber Tone Edge in a small tip opening - even a 4 or 4*. What's nice is that as they develop, a similar mouthpiece can be had without a greatly different embouchre in a larger tip opening. The Tone Edge mouthpieces have a large chamber which prevents them from being too bright, but those mouthpieces are finished rather inconsistently - particularly the facing and baffle shape. So some will sound brighter than others - possibly unsuitable for a concert band, but not necessarily. A safer bet would be a Yamaha 5CM in hard rubber. Similar in design to the Selmer S80 mouthpieces but more affordable, generally. Slightly more open than the 4C, but manageable and with a warmer tone.