And some correctional institution already have programs like that but they work on a voluntary basis since they can’t waste time and money on people that don’t want to learn; also “problematic” inmates would create a bad environment for those who really want to learn.

EDIT

OK, going back on “how the average Joe make a law”:
> First you need support from the community (nobody is going to care if your idea is rejected by 99% of the community) so you need to “sell” you idea to the community and asking them to sign a petition.
Also if you get the support of reputable civil groups would help.
> You need to support your arguments with verifieble data (so you need evidence to support your numbers of: no High School Diploma = 92%; percentage of inmates who return to that facility = 73%)
> You need to clearly articulate the benefits that such a law would bring to the community.
> More importantly you need to convince the people that actually make the laws (state legislators, congressmen and so on).

So in simple words: it’s a lot of work and long road.