The youngest that I can remember my Mother privately tutoring on piano was an 8 year old, a girl that she continued to tutor until the girl went to college. That girl was one of two that played the xylophone in our high school marching band and the pianist in our concert band, graduating in my class. In college she became a dietician and was employed in a hospital until she became a casualty in an auto accident that prevented her working. When we closed our home, she bought my Mothers' Iver's and Ponds folded spinet piano. The last I heard from the girl, a note in 2015 X-mas card ... now a crippled geriatric woman, she was still tutoring other children on the piano. FYI she had been hit by a ambulance arriving at the hospital as she was leaving for the day.