Take my advice and hire rather than buy. The school should be able to get you in touch with the right people. It will be decent equipment and when if your DS decides he's not actually interested/his fingers hurt/practice is boring/he's rubbish at it then you won't have an expensive instrument lying around.
My 12-year-old DS wants to learn bass guitar, and we will need to get one quickly if he is going to join the beginners class that he wants to join. I know nothing at all about bass guitars, so any advice appreciated. Obviously, don't want to go over the top price-wise given that we are buying for a beginner, but equally don't want to make the mistake of going for cheapest option if that will be complete junk.