“Is it OK for us to have a party with both boys and girls?” New Era, Aug. 2013, 42
You and your friends shouldn’t have any worries about holding a gathering of boys and girls as long as it meets a few conditions: (1) There should be adult supervision at the party, (2) the boys and girls should not be paired up with each other at the party so that it seems like a dating situation, and (3) the atmosphere (music, language, activities, and so on) at the party should be in harmony with Church standards, allowing you to feel the Spirit while you’re there.
Some ways to ensure that these conditions are met are to include parents in the planning of the party, plan activities that keep people interacting with the larger group, and hold the party in a common and contained space so that people are discouraged from pairing off by themselves. At any age, occasional parties with friends who have similar values can be really enjoyable. At your age, you just need to focus on having fun together in a wholesome and safe environment and avoid any sense of dating or pairing off.