When This Was?

One of my students is from Africa. English is his first language, but he speaks with an accent and is sometimes hard to understand. Periodically I post their grades on the wall and he was curious when I had last updated the wall.

After school during tutoring he pointed to the grades and, complete with his accent, asked, "When this was?"

Another girl in the room started laughing and unabashedly added: He just said "when this was."

I refrained from reacting until he responded, "What? Why is that funny?"