Ivy and bean make the rules (Chronicle Books)

It's Spring Break and Bean's older sister, Nancy, is going to Girl Power 4-Ever Camp, where she will do Crafts and Music and Dance and other secret things that Bean will never know about because you have to be eleven to go to Girl Power 4-Ever Camp. Bean doesn't care. She doesn't want to go to camp. She wouldn't go even if they begged her. Bean and Ivy can make their own camp--their own better camp!--Camp Neanderthal Flaming Arrow.