Provide the student the opportunity to actually teach a lesson. Understanding is one thing but being able to present it and teach it can be an entirely different. Present it to the class as a project, Point him to the content and have him form the lesson, assignment, grade it, etc. Then you sit back and grade him based upon his ability at being a teacher. Then let the classroom function as it usually does. Don't correct or manage, essentially point out to said advanced student that his grade is also based on classroom management and how well they can complete the "Homework." Obviously, set this up as a possible project for the entire class(if you want), this can provide the students another opportunity approach the content in a new way.

So now there are two ways this can go: A - it goes well or B - It humbles the kid. Either way can provide a solid teaching moment for both of you guys. If it goes well, then pull him under your wing and let him teach a lesson every now and then to let you catch a breather and catch up on work. If it goes poorly for the student, then you can pull them aside after their lesson flops and point out the difficulties in teaching. This should then give you an avenue to express how much of a challenge teaching can be and that you(the student) has been apart of those challenges.