legacy/admission?

I went to Penn undergrad and have a son who’s a high school junior. He’s interested in applying there. My understanding is the legacy only gives you a boost if you do ED, correct? How much of a boost is it? He’s a very, very strong student. No one is a shoo-in there, but he’d be pretty competitive (average well over 100, SAT in the 2300’s, good EC’s, etc.). I’m trying to decide if we should do ED there: it’s one of his top choices, but there are other schools he’d like too.

You are correct. They only do legacy during ED. The boost can be huge. Someone mentioned in other threads that the admission rate in ED for legacy can be as high as 40%.

Yes the boost is huge. I myself am a legacy applicant (senior in high school) with stats a tad worse than your son, and I can confirm that the admit rate is only boosted during ED and the rate is between 40-45%.