Importance of Preschool

I think this study is partially skewed because educated parents understand the importance of learning from birth and are more likely to send their kids to pre-school. That's just my take. What do you think?
FROM NBC: A good education at age 3 may pay dividends decades later. A 25-year study of more than 14-hundred children finds those who were in a high-quality preschool as young as age 3 were more likely to go farther in school and have a higher socio-economic status as young adults.
They also had lower rates of substance abuse and incarceration. Study participants were low-income children who were involved in a publicly-funded early childhood development program in Chicago. Biggest benefits were seen among male children and those whose parents were high school drop-outs.
-NewsAnchorMom Jen
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