There are several ways you can refer to homework that is assigned during the lunch hour in Engpsh:

Noon homework
Lunchtime assignment
Midday task
Afternoon assignment (if it is due in the afternoon)

For example, you could say:

"I have to finish my noon homework before my afternoon classes start."
"I'm going to take a break from my lunchtime assignment to grab a bite to eat."
"I'm almost done with my midday task. Just a few more problems to go."
"I have a lot of afternoon assignments to complete today."

I hope this helps! Let me know if you have any other questions.