Roles and permissions

I have the following problem: We manage all accounts with LDAP. Teacher at our school are automatically assigned the "Course Creator" role, because they should be able to create courses and there are too much to assign the roles by hand.
But because the frontpage is also a course, they can change everything on there, especially add blocks, and that is not what we intend. How can I restrict that while still let them create courses?

Thanks a lot in advance for any help...