user permissions

Hey, ppl
Right now i’m working on a little blog for comunication between teachers and students.
Administrator is me, there is a role for teachers and one for students. My idea is let the teachers use propel as a tool for set tasks and let the students change just the % of the project tasks (if the task was assigned to him).
I know this need some programation, still no sure how to do it really, but i want start trying to give the different roles some permissions over Propel.
For example: Teachers can add and modify tasks, and assign them to a user (student)
Students: just can modify % on their assigned task’s (this part i guess need to be added by me)
I’m using a role manager plugin, but can’t get it to work with propel, cause i don’t know what privileges add for it work with propel.
(plugin name: User Role Editor by Vladimir Garagulya)

No sure if i explain myself well… but thanks in advance, and excuse my english.