By 8 years of age they have been working as some level of field hand for a couple years, especially on the more "strict" plantations. 90% of them have seen a family member either killed or been shipped off to a "more rigorous" location or sent to the Reich as a factory worker.
By the time a Polish, or Ukrainian or Latvian, etc. child can pass the most basic logic test (such as the big/little cup choice) they understood that they were doomed and had no hope of a future that would get better. Needless to say but when the WAllies defeated the Reich they had masses of 12 & 13 year old orphans who were also effectively sociopaths with negligible education no useful skills on a modern 1960 era farm.