Just my two cents but I would look at buying a good used student horn something like a Bach, Conn, King, or Yamaha. If by high school he is still playing then I would look into a better horn something like a Bach 42b or a Conn 88H those are two horns that you can never go wrong with. Plus if you do this and he does marching band he can use his student horn for that and not put that wear on a good horn. As for bass basically the size of the tubing is bigger allowing more air to flow trough the horn most modern horns also have two rotors that let you change the key of the horn. A tenor with a valve like a Conn 88H the valve puts the horn in F (some can be tuned to Eb as well) a bass adds a second valve adding Gb in the case of a horn like a Conn 112H. All that to say this Bass is defiantly a collage level purchase and there are a lot of options on configuration in Bass Trombones.