Positive peer pressure
Having a student model a piece of music is always far superior to an adult piano teacher. If the friend is playing then they are confident they can play as well. Built in ensemble playing - In a group situation you have ready-made ensembles without having to schedule special times for this experience.
Repetition is easier
More time with the teacher in a group setting. This allows for more time for repetition. Clapping rhythm over and over alone is boring. Try it with some friends. It then becomes a game!
Counting out loud is socially accectable
When students count out loud together, it becomes socially acceptable. Counting out loud in a private lesson is uncomfortable and embarrassing. This is an important habit for rhythmic skills.
Ability to observe the teaching process
Students must become their own teacher when they go home. In a group lesson, a student learns this process by observing other students. They leave with a dual educational experience. They are a performer and a teacher.
Perspectives on any challenges of learning piano
The development of self-esteem is essential. When a student takes a private lesson, they have no perspective on any challenges they may encounter while learning to play the piano. In a group situation, they can hear other students playing. Instead of thinking that something is wrong with them, they realize that most challenges can be overcomed by simply practicing more.