How do I encourage learning to an underprivileged group
You have a program that sounds almost too good to be true (e.g., free classes, free software, free books, no contract).  And your biggest challenge is that you cannot find new students, right?  Well, two things come to mind.  First, there is a "catch" -- that is, when it is too good to be true, it probably isn't true.  Are there any hidden costs or problems with the program that you have not shared or identified?  Second, what is the extent of the mismatch between the objectives of this program and the needs, values, and interest of your target group?  

My recommendation would involve careful analysis of both questions.  You are likely to find a lot of good information by following up with those who have dropped out. Ask them why they dropped out.  Barriers to attendance?  Then you need to figure out why more people aren't signing up.  Consider surveying individuals who were provided the information but chose not to sign up.