Have a look at Sal Khan's latest project, https://schoolhouse.world/ https://schoolhouse.world/ It's focused specifically on math at the moment, and takes a mod

Have a look at Sal Khan's latest project, https://schoolhouse.world/ https://schoolhouse.world/ It's focused specifically on math at the moment, and takes a model similar to what you're proposing. Volunteer tutors give lessons, and students are encouraged to pay-it-forward and become tutors themselves once they master the material. They've had thousands of students already and are working on scaling up a few orders of magnitude right now.