This link is concerned with overly academic preschool programs called "prekindergarten". It's a controversial program which this study debunks. It shows that it is detrimental if not ineffective. Here's a direct quote.

“Prekindergarten increases reading and mathematics skills at school entry, but also increases behavioral problems and reduces self-control. Furthermore, the effects of prekindergarten on skills largely dissipate by the spring of 1st grade, although the behavioral effects do not.”

This is NOT a traditional preschool early education program. This program represents an attempt to misapplied adult educational priorities on children. The study is not concerned with tradional early ed program other than to say academic oriented programs do not provide a lasting academic advantage and these programs cause long term emotional damage to children. The study does NOT say that kids with NO good home care would not benefit from a traditional early education program - Keolu's lie.