The museum usually makes plans with the group's coordinator ahead of time. If your teacher said to bring a lunch, I'm sure it would be fine. Just ask your teacher if it's ok if your lunch has to be refrigerated. Or you could put an ice pack in your lunchbox to keep it cool. Have fun, it's a great place to visit.
You can bring lunch, but you'll only be able to eat at the cafeteria. They don't allow food on the wings. Your teacher most likely will have a designated 'lunch' time.
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