When my son was in 6th grade I decided I was going to do everything I could to make sure he didn't start Jr. high as 'the fat kid.' He did Atkins and lost 40 or 50 lbs. He was still overweight but was at least able to get into his first pair of jeans, ever. BUT - to do that it took an absolute Iron grip on my part as to what went into his mouth. He regained that weight back over the next year or so even though I still tried to follow the Atkins rules.
Once he got his drivers license though was when he really went to town on the food. He'd chow down on the way home from class or on the weekends. Sometimes he'd even leave the house at night to go get food because I generally try to not keep 'forbidden' things around. At this point he is hoping the lapband will help make it so he's not 'always hungry.'