Our daughters go to The Music Conservatory (in Flower Mound, but I beleive they have a Frisco/Plano location). My oldest one started about 4 years ago, and my youngest 2 years ago (they were each 5-6 years old).
One of the great programs they offer for the young beginners is a "lab class." It's a one-hour, once-a-week, small group of students (usually 3-6 kids). They're in a room with 6 pianos and one teacher. Each week the class is separated into a few segments: kids will play their homework piece(s) for the teacher and get a new assignment for the following week, kids will meet in a group at a table to play fun games to learn sheet music and notes (they clap to the written piece, or shout out A-A-G-G-F-E-D when the teacher points to a measure or line, etc. Then, at the end of the class, they play pieces together, with the less advanced students playing the simplest parts of the songs, and the more advanced students playing the more difficult part of the songs. This seems to help everyone work on their timing, as they have to play with the group.
Kids have headphones, so they're not disturbing each other while they're playing the homework pieces in the beginning. They also break into teams for some of the games and get stickers at the end.
I think they suggest their lab classes (which are also cheaper than private lessons) for 1-2 years before moving them to private lessons, and kids can join any time during the year (hence the reason there are more and less advanced students).
I'm sure they can explain the lab system on the phone better than I can in writing.
Good luck!