One on one "tutoring" is the most effective way to make early education productive and it's not even close. Even the outcomes of parents spending 20 minutes a day reading to their infants and toddlers correlates with better educational outcomes. and I'm sure there are many here that share my own story. The only reason I was somewhat academically successful was because my mother took the time to teach me how to read when I was 3-4. Without that early literacy, I'm sure I would have never been able to achieve anything I've done, especially with ADHD. By the time I was in kindergarten, I knew how to read already, but, even there, reading was taught 1 on 1, with students taking turns with the teacher to learn. I don't think that's done anymore at most places, especially when you have 30:1 teacher ratios. 5 year olds can be way more capable than we give them credit for, but they need personal attention.