The effect of earlier and longer exposure to public preschool on Behavioral and Developmental Health

This study finds that preschools facilitate early diagnosis and treatment of conditions that can hinder learning. 

Low-income children born shortly before their state's school-entry cutoff date are 16.9, 9.3, and 14.8 percent more likely to be diagnosed with Attention Deficit Hyperactivity Disorder, a speech or language disorder, and a hearing or vision condition at ages three and four, compared to children born after the cutoff. They are also more likely to receive downstream services. 

These findings emphasize the role of earlier and longer exposure to public preschool in driving diagnostic gaps previously attributed to elementary school-entry and within-grade peer comparisons.