E Learning System for Music theory

I have a need to create an E classroom for teaching and testing on music theory.

I have 20 or so 2-5 min videos, each followed by a multiple choice exam.  I'd like students to log in, take exams online, and have the ability for teachers to track performance.

We are starting with 7 teachers in my district, each having 500-1000 students.  Each student must log in to their teacher/class and log performance and progress.

Each teacher will expect their students to complete the entire course of 20 videos/tests by the end of each semester.

After this fall, we plan on expanding to the entire state, and then region.  There could potentially be 100,000's of users.

Each district or teacher will pay for their yearly/monthly subscription to this curriculum, so we'd like to have a "pay online" function.

We need some help with this project and not sure if Moodle is the answer.

What do you think? Any comments or advice on which LMS to use? We wold like someone to partner with to help branding, support, and training.  

I've heard Moodle is the best.  Any recommendations?

Thanks,

Eric