My youngest son, Nathaniel, went to a wonderful preschool/daycare for a long time. Doodlebug was the best a mom could ask for. The owner, Miss Mandy, taught the kids letters and numbers, and let them make messy art projects full of paint and glitter and glue.
She also designed a schedule so they would learn about a new subject every two weeks. She and her employees were a dream and made sure the kids understood everything. It normally worked.