i see great social advantages in boys and girls in classes together. they learn how the other half lives..kinda.  they already get into the "us VS them" mindset .. keeping them apart doesn't sound like the answer. it sounds sexist - for both sides.  boys are slower to develop..putting them in a classroom with younger in years, but equal in maturity girls?  not the answer either..  
 both nature and nurture create the most heinous people it seems. and sometimes these lifetime criminals reach an older age, and are just determined they are not going back to prison... at all costs - they eliminate the victim/witness, shoot it out with cops or take their own life. i believe some people are just born predators and can't be changed. they may learn and be aware, and control it and be successful in "passing".  others love the hunt.
 anyone who's spent time behind bars and truly rehabilitates - more power to them and it's a shame it is so tough for them to just get a break in life afterwards.