I know on BA if you wish to do this and your children aren't old enough to travel alone then you have to pay the unaccompanied minor fee

I once sat next to a couple of teens (about 13/14) on a flight from LHR-LAX on VS in Y who's parents were in Business, they were friends and one of them shared that her friend's parents couldn't stretch to have all 3 in business and while her parents could have done she'd chosen to sit with her friend, they were allowed to visit once and their parents sent gifts down to them via cabin crew but they didn't come down to them