This sounds like a very fun project. Let me give you a few ideas by way of giving you several sentences, which you can use as a springboard for other ideas.
- Lunch hour at my school was like a swarm of busy bees flying around in pursuit of sweet honey. All the boys and girls were hungry and anticipated their food.
- The wait for the lunch bell to ring was tantamount to horses waiting to be let go to run their course in the big race. The anticipation in the air was nearly visible.
- Lunch hour was chaotic, but it worked. In less than thirty minutes every day, everyone ate, talked, and got a break. It just worked. It was like a an abstract painting that was at the same time without form and with form.
As you can see, you can take one idea or thought about lunch time and look for analogies. The sky is the limit when it comes to metaphors and similes.