There are many contributing factors to education success. These kinds of analytics often isolate one factor, so the end picture is skewed. It is my belief that early education is a very good thing. So much so I put up my own money and started a school with my friends/partners from Asia. Smallest project I did at the time and way out of line with my infrastructure life. But pre school through high school, from the start. It's ranked quite highly now, and everybody takes credit for my development work, but I don't need fame. I watched children become wonderful thinking adults. The elements I think important: (1) stable and safe home environments. (2) Building character. The headmaster once told me he's more concerned about good character than grades. And he was right I think. (3) Early education, like preschool, including foreign language. Noted that children need to be taught skills to enhance learning later on. Often kids entering later grades couldn't keep up with the others.