I honestly think anything younger that middle schoolers cutting weight is ridiculous ( even then it should be low amounts). I think everyone is entitled to do what they want though. It's another thing if the kid is hefty and simply regulating thier diet to a healthier one helps them drop down a little. But trying to bring a kid down to a very low body fat /weight ratio while thier body is actively growing and maturing is not the most advisable thing to do.