Which is considered by many to be a form of human trafficking.
My own family history has a lot to do with indentured servitude. If you watch Korean historical dramas, you'll find the condition described as being a "servant" but at other times, the same condition will be described as being a "slave."
In terms of being signed up as minors, exactly how do you draw the line? I went to a boarding school where they didn't let us off school grounds without getting leave.
Just because you signed a contract doesn't mean you shouldn't be able to get out of it. I'm not entirely certain where to draw the line.
How about physical coercion? Did 19 year old Jackie Chan consider himself a slave? Was he kept in a place through physical coercion and torture? Did he dream of jailbreaking himself out of his barracks and wire-cutting the fence and running to freedom while being chased by guards prepared to main or shoot him? Or was he thinking of it as working through a contractual debt?
The line should be firmly held at physical coercion. As always, there will be people who skirt the lines by coming up with things that have the same effect, but which are "technically not coercion."