This is the classic people BINGO (Find someone who...) game, except it has a math twist. Students have to figure out simple calculations before they can find a classmate who has siblings, is wearing a certain number of bracelets, has been to the Emergency Room...this would be a great introductory activity for a first day of school activity. Even if you don't choose it as a back to school activity, it could be used during any time, even a fun morning work thing. The idea is to get four signatures in a row to make BINGO, but also to fill the whole entire card.
There are four BINGO cards, one specific to grades 2-5. Each one is aligned to typical grade level expectations from the year prior...which means you could even differentiate this back to school activity by asking students to challenge themselves!
All you need to do is print enough copies for your students, ask them to grab a pencil, and then let them move around, chat and find out about each other!