I haven't found the point about learning from one's mistakes but this is the closest Mao quote I've found:
Which roughly equates to something like:
Our prisons are not prisons of the past, our prisons are actually schools, they are factories, or farms.
Jean Pasqualini might have taken some liberties or licenses since this has to do with 劳改 (re-education through labor) with his translation, but I can't be sure yet.
Update: So, the wiki quote is listed as:
Behr, 1987 p.283
Which is a reference from Edward Behr's 1987 book "The Last Emperor" - page 283, here is the excerpt in question:
The difference lay in the overall approach of those in authority to all those accused of any kind of 'crime'. As Jean Pasqualini, author of Prisoner of Mao, a uniquely insightful analysis of the Chinese penitentiary system based on his own prison and labour camp experiences, put it: 'Prison is not prison, but a school for learning about one's mistakes.' Chinese prisons were places 'where the prisoners reform the prisoners'.
A translation of "The Last Emperor" (中国末代皇帝) was done by 黄群飞 (Huang Qunfei) and published in 1989, here is his translation of the above paragraph found on page 219 of the book:
Jean Pasqualini's quote is quite the resemblance of Mao's by saying: