I hear this statistic a lot as some kind of indictment of our education system, but if you think about it, it makes sense.
Wow, that train of thought has completely blown me away. I am not even sure on where to start replying to you.
If you spend more on education, not just tertiary, but primary and secondary, it will nurture youth to have higher aspirations, it will teach them more. If you have someone leaving secondary school with a good understanding of basic subjects (math, English, at least one science and computers) as well as a rounded splash of some elective subjects such as history, economics, art, music, religion they are much more likely to either look for further education on their own (even if they have to pay as much for it as in the US) and move on to being a productive member of society rather than ending up in prison.
That's not to say that everyone with a good education will never do anything illegal or end up in jail, but the number of people in prison with a poor education should stand out above anything else that to keep people out of prison, give them an education. Give them the ability to actually join society as a peer rather than as the bottom of the ladder cleaning the bathrooms or working as a parking attendant.
This concept of paying more earlier also has the advantage saving more money in the long run. If you don't need to pay for putting someone in prison AND have the benefit of that person contributing to the society they live in, it clearly is a win-win scenario.