Melatonin to help kids sleep?

My older kids have always stayed up late. I’ve tried everything, cutting back tv/electronic time. Sending them to bed early etc and no matter what I do even waking them earlier they still goto bed around 11:30. ESP my oldest who some nights will but up until 12-12:30 (she’s 8). A friend suggest melatonin, as she uses it for her son. But mentioned it doesn’t work for every child. And can actually have an opposing effect. Obviously I’d consult with peds for a proper dosage. I just want to know what other moms experiences have been with it. Whether it’s worked for them or made things worse. Thanks