I am not sure I expressed myself clearly Granny Bee, but I agree with what you have said. It is true than many people end up in prison because they have missed out on positive intervention in the early years.
Jackie, Young Offenders Institutions replaced Borstals, and compulsory education is part of their programme. I've heard people say that it is sink or swim in some of the YOIs so it must be very difficult for timid young people. They take people up to the age of 18 but if their sentence is long enough they can then be transferred to an Adult prison. Borstals were for up to aged 21 years. Don't take this as gospel but I have a vague idea that once they reached 21 the sentence was over and they were released with possibly some outside supervision.
A major fault throughout the system is that prisoners are able to build their little kingdoms with few repercussions. They are a lot brighter than 30 or 40 years ago and know their "rights". Prisoners fear their peers far more than they fear the police , prison staff, or public disapprobation.
I've taken so long over this post, trying to do 20 other things at the same time, that the discussion may well have moved on by now.