Hello,

Are both Past Simple and Past Continuous verb forms acceptable in the following sentence?

"When the teacher [looked/was looking] out the window, he slipped a note to his friend."

a) When the teacher looked out the window, he slipped a note to his friend.

To me, the Past Simple form implies a sequence of action. The teacher looked out the window. Then he slipped a note to a friend.

b) When the teacher was looking out the window, he slipped a note to his friend.
c) While the teacher was looking out the window, he slipped a note to his friend.

Can the action of looking out the window be the background if "look" is in the Past Continuous form? Or for the sentence to make sense, I would have to change from "when" to "while"?

Do "when" and "while" in these sentences differ much in meaning?

Thank you.

Nawee