Letter of recommendation for wait list school

I was wondering if submitting an additional letter or Rec may help for getting off the wait list at a school? My nephew was waitlisted at his first choice school for engineering and he could possibly get a letter from his dual-enrollment calculus teacher. But I know some schools (like USC) ask that students not send an additional letter of rec. If a school doesn’t actually say no more letters of rec, could one more possibly help?

Not that USC has a wait list (I think this was in reference to appealing or going from spring to fall admission- he was rejected from USC outright- just using it as an example of a school that says no more letters of rec)

I’ve never bumped before-but bump. Any suggestions?

I would call the school and ask. I think a few schools would accept it, but most wouldn’t. I think they just want to see a letter stating the applicant is seriously interested and any updates they may have now since they submitted their application.

Try to find out who in Admissions read his application, and yes, send worthwhile updates and any additional rec that can speak to something not already covered in the app or other letters!!! Good Luck!!!