Is kickboxing or boxing a sport?

My mom wants all of us (Children) to be well rounded, all I need to do that is a sport. I really want to do kickboxing or boxing since my brother joined the boxing team at his school but he doesn't take it seriously though, so I thought his boxing equipment would be a waste. But my mom said, kickboxing is only for losing weight, and that boxing isn't a sport. She just says "If I say it's not, then it's not" and I mean, I really wanna kickbox, since I'm one of those teens who's hormones make them angry and in rage than h0rny.