Oral language comprehension skills are foundational to building reading comprehension. Thus, early instruction designed to develop oral comprehension skills may benefit long-term reading outcomes for children in early childhood education classrooms. With that in mind, Lo and Xu conducted a randomized controlled trial to evaluate the effect of Let’s Know!, a language-focused, supplementary curriculum, on prekindergarten and kindergarten students’ vocabulary and comprehension outcomes.

The intervention consisted of providing students with four 30-minute class lessons per week that focused on specific language skills. The program was designed to be administered over 25 weeks. Study participants were 69 prekindergarten classrooms (n=361 students) and 56 kindergarten classrooms (n= 328 students) randomly assigned to a treatment or control condition. Classroom teachers in the treatment condition taught one of two Let’s Know! versions: Let’s Know! Broad and Let’s Know! Deep. Both versions were designed to improve language comprehension based on the simple view of reading, which posits that reading comprehension happens when students have both language comprehension and word decoding skills.

In their intent-to-treat analysis, Lo and Xu found that the students in the treatment condition outperformed those in the control condition.

• Prekindergarten students in both Let’s Know! conditions outperformed the control condition on vocabulary and comprehension monitoring outcomes (ES=+0.55 to +1.22).
• Kindergarten students also showed significant gains in vocabulary and comprehension monitoring outcomes (ES=+1.01 to +1.55).

The study did not find evidence that Let’s Know! had a statistically significant effect on other targeted comprehension-related skills such as story grammar or understanding expository text. However, the study’s results show promise for the targeted vocabulary instruction component in Let’s Know!. Additionally, by improving comprehension monitoring, Let’s Know! may impact developing reading comprehension skills.

Source: Language and Reading Research Consortium, Lo, M.-T., & Xu, M. (2022). Impacts of the let’s know! Curriculum on the language and comprehension-related skills of prekindergarten and kindergarten children. Journal of Educational Psychology, 114(6), 1205–1224. https://doi.org/10.1037/edu0000744

Note: The comprehension monitoring probe assessed children’s abilities to monitor their understanding of orally presented narrative or expository passages.