I just turned 6 when I started first grade. Kindergarten for me from 4-5 yo was at a big table in the family room where my Mother taught me how to print and write cursive, basic Math, Reading, Arts & Crafts, etc.
Walked up the street to the first kids house. She was 7 and in second grade. She was in charge. Up a few more houses to another first graders house. Then on to another second grader... by the time we got to school there were 5 of us, lol. All between 5-7 yo. Did that routine until Middle School (6th grade). Then walked a different direction. Same routine, different kids.