Tell him about his other opportunities (although perhaps being on AoPS he is already aware of them). Summer programs like
and others come highly recommended, and several of their alumni are here on MO! , even. (Full disclosure: I went to PROMYS myself.) In a few years I would also recommend that the student apply to the Research Science Institute. (Full disclosure: I also went to RSI.)
When I was in a similar position (or so I flatter myself!) I would also have appreciated being introduced to the math blogosphere earlier (which I didn't discover until freshman year of university). Tim Gowers (minus the recent Elsevier stuff which is a little less relevant), Terence Tao, and John Baez are all great places to start.
