Dein Lehrer hat recht, Du nicht.

I'd say: "cross on red"

"jaywalking" is another possibilty.

Werner, ich dachte, "jaywalking" wäre das (verbotene) schräge Überqueren der Strasse, egal on Ampel oder nicht...

Beides.

Nicht nur schräg, einfach irgendwo, oder bei Rot, idR ohne zu schauen :) Also quasi "illegal or reckless pedestrian crossing", egal wo und wie.

Aha, danke. :)

crossing while it's red
crossing during red
crossing when it's red

@sundancer, Your teacher is likely wrong.

This whole topic has nothing to do with "jaywalking", absolutely nothing.

(Very separate issues.)

AE

cross on red

würde ich sagen.

@8:
Don't you say "on red" in this context in the U.S. then, opine?

I don't.

I'd say:
-- at a red light
-- when it's red
-- if it's red

I don't use "on red".

"to cross on red" is definitely correct. Similar to the "right turn on red" which is permitted in some states - and was a hard habit to break when I moved to Germany!
"At a red light" I would say if I, or the car, were stopped: "I was waiting at a red light."

I wouldn't say "to cross at a red light." That sounds like a red light that is just there, rather than a traffic light that happens to be red, but will change to green.