One back to school activity students worked through at the beginning of the school year was "Survival Island". (Idea from the book Teach Like a Pirate.) Students have to decide who gets to stay on the island and who gets to leave the island with the hope of being rescued.
Students come to understand that we are all contributors to the group. We may have strengths and weaknesses that we bring to the group. Working together and listening to each other is key!
Another team building activity is the "Paper Circle" challenge. Working in small groups, students are provided with 2 pieces of paper, 2 pairs of scissors, and one glue stick. They are tasked with creating a paper circle that everyone in their group can stand in when completed.
Students have to communicate, assign roles, take turns, share, and negotiate with their classmates in order to complete the task.