Ask HN: I got into startup school, co-founder did not. Should he come?

I would agree with you. First of all, proximity does matter. I'm working via Skype with my co-founder and technology makes this a pretty painless process, but there is nothing like good old-fashioned face-to-face interaction. Second, you're right - networking opportunities are important and your chance of finding the right ones increases greatly. Congrats

I say yes only if you're staying for more than one day in SF, and you have other networking activities to do. That way, his time isn't wasted if he does come.