Page three of X-MEN #1 by Jack Kirby and Paul Reinman.
There’s a half-erased border note at the bottom, written by Stan, that reads:
BE CAREFUL TODAY, ANGEL. THIS IS YOUR PROBLEM IN WING REFLEX & SPEED. LET’S SEE HOW YOU DID ON YOUR HOMEWORK.
It’s astonishing how little background there is in most of these panels. Kirby would have been cranking through pages very quickly at this point.