The abstract for the paper, which is authored by Philip DeCicca and Justin D. Smith, reads
We investigate short and long-term effects of early childhood education using variation created by a unique policy experiment in British Columbia, Canada. Our findings imply starting Kindergarten one year late substantially reduces the probability of repeating the third grade, and meaningfully increases in tenth grade math and reading scores. Effects are highest for low income students and males. Estimates suggest that entering kindergarten early may have a detrimental effect on future outcomes.Now that is a result I would not have guessed and I would love to know the psychology behind it. If correct the result does raise interesting policy issues to do with when we start children in education.