The Truth About Group Piano Lessons
The truth about group piano lessons is that the teacher's attention is diluted. It doesn't matter how much talent and charisma the teacher has. Learning the piano is a very attention consuming effort. This is true for children as well as adults. I have been a supervising instructor for group piano classes for a major national instrument company. I can honestly say that while adults might be able to benefit from these kinds of lessons, kids find it particularly difficult to get the attention they need. This is true especially at the very beginning when they need the most individual attention.
Twenty Kids In A Room
In a group class, kids will be kids, and left unattended they will distract from the other children's efforts. We all know there are kids who disrupt the class. Even a little disruption can make a piano class all but impossible. However, I've never seen an adult be anything other than attentive during a group class. The only drawback in this case is how much attention you receive from the instructor.
Adults Do Better With Group
It's for this reason that I think adults will get more out of group piano lessons than will kids. I'm sure you're looking at the alternatives. One of the primary reasons for considering group piano lessons is the lower cost. So you may be saying, "Why not just get a cheap piano teacher?" This may seems like a good idea at first, but who are the "cheaper" piano teachers?
Get An Experienced Teacher
In my experience, they are generally very young people with good intentions but very little experience with children, adults or teaching piano. I would suggest that you visit the group piano class in question, ask if you can observe, just as I would audition a private piano teacher. If your reaction is, "How can anyone learn in this situation?" it is likely that you or your child would have difficulty, too.