Which is also legal in some places of Europe, it's called "practicing" or whatever.

I think the system in Europe is more about practicing skilled trade than just doing unskilled factory work. If this story was about kids apprenticing to be plumbers, then I think there would be much less outrage.

Depends on the course, same practical internship are pretty much of the level of unskilled work. Still not okay without at least a decent pay if you ask me.

I don’t think 16 and a half kuai is very decent, but these kids are mostly from rural areas so it might seem like a good deal to them.

I do not know how it is now, but when I worked with companies doing apprenticeships for electricians in the Netherlands a while ago, I noticed most of them (the “children”) did unskilled or no work at all and did not care because the company signed off on their work so they would graduate.