How do you go about doing that? The school I’m applying to (Cornell) only has two slots for recommendations.
Cornell very strongly recommends limiting recommendations to two (which is why they only accept two on the common app). If you want to send more, you have to send by snail mail.
It means they probably don’t want more than two, so there’s no point in sending extras. Just like colleges that don’t want any – if you send them, they aren’t going to do anything with them. In fact, if it came down to you and another applicant head-to-head with all other factors being equal, I’m willing to bet they’d rule in favor of the applicant that actually followed directions.