Sebastian is yawning? Hmm...

You are a music teacher and give private lessons on a few different instruments: guitar, autoharp, piano. A 7-year- old begins coming to you for guitar lessons. He seems to be a bright, receptive, highly motivated child. 
        The first time Sebastian picks up a guitar, he looks like a guitar player! His posture, demeanor, the way both hands assume a comfortable position—it all seems right, as though guitar playing were already psychically known to him. Whatever technique you model, Sebastian picks it up quickly. You give him the starting note to a familiar tune and he is able to figure out how to play the rest. He easily learns the chords you show him, and is able to find the chord changes to simple songs by ear.
        Over the two months he has been coming to you for a weekly lesson, you have introduced the fingerpicking and chords needed to play more challenging songs. Sebastian’s parents are thrilled with his progress, and are hoping that he might perform one of the songs in his school’s upcoming talent show.
        As you observe Sebastian’s learning style, you begin to notice a pattern. He approaches a task with intense concentration, but at some point, usually 10-15 minutes into it, he begins to lose focus, fidget, yawn … At this point, if he tries to continue working, he makes more mistakes, missing transitions from chord to chord—even having trouble with passages he played perfectly well before. As Sebastian’s teacher …

What would you do?