This study is a randomized control trial of full- versus half-day prekindergarten (pre-K) in a school district near Denver, Colorado. Four-year-old children were randomly assigned an offer of half-day (4 days/week) or full-day (5 days/week) pre-K that increased class time by 600 hours. The full-day pre-K offer produced substantial, positive…

We investigated whether individual differences in overall receptive vocabulary knowledge measured at the beginning of the year moderated the effects of a kindergarten vocabulary intervention that supplemented classroom vocabulary instruction. We also examined whether moderation would offset the benefits of providing Tier-2 vocabulary intervention…

A two-cohort cluster randomized trial was conducted to estimate effects of small-group supplemental vocabulary instruction for at-risk kindergarten English learners (ELs). "Connections" students received explicit instruction in high-frequency decodable root words, and interactive book reading (IBR) students were taught the same words in…

This paper reports the fifth-year results of a study comparing the English and Spanish language and reading performance of Spanish-dominant children randomly assigned beginning in kindergarten to Transitional Bilingual Education (TBE) or Structured English Immersion (SEI). This is the first randomized study to compare TBE and SEI reading…