Prison Break Star Giving Acting Lessons In Jail

Sources tell TMZ, the L.A. County Sheriff has Lane mentoring about 20 prisoners as part of the "Merit" program -- designed to teach marketable real-world skills to inmates.

In addition to acting, we're told Lane is also giving a crash course in screenwriting as part of the program.

And get this -- Lane's so moved by the experience, we're told he's promised the Sheriff to continue to mentor the prisoners even after he's been released ... whenever that is.