Отданные в обучение в город

In an article abt the poor condition of life for children in XIX century in Russia I see:
Отданные в обучение в город к жестоким и грубим хозяевам, они проводят свою жизнь в непосильном труде.

The first words that I can't understand in the context of the article:
"Delivered to the instruction ... for cruel masters...". I don't understand.
Thank you.

Delivered into the apprenticeship under cruel masters they live their lives in hard labor.

Thank you.