Meta-Analysis:

Inclusion Criteria:

I included any study with a control group that either had a calculated effect size or provided the raw data, making it possible to calculate an effect size. I examined each study listed on the CKLA research website and the Amplify research website. I also searched the academic databases Education Source and Sage Portal, for the terms “CKLA”, “Core Knowledge Language Arts”, and “Amplify CKLA”. Each study found had already calculated their own effect size. There were no additional studies found in each database. Mean effect sizes were then calculated and displayed in as many ways as possible, to give the reader the most options for understanding. Effect sizes were not weighted to sample size. This study is not peer reviewed. 

Studies Included: 

Wedlman, Et al, published this study in 2004 comparing the average performance of 5 CKLA schools to the US average. The study was unpublished and reported moderate differences, but smaller standard deviations. No effect size was calculated or could be calculated based on the statistics provided. 

Cabell, E al, published this study in 2009, and compared providing students with background knowledge to not giving them background knowledge. The study only looked at background knowledge and vocabulary outcomes for k-5 students. This study was listed on the Amplify website as proof of concept. 

Cabell, Et al, published this “meta-analysis” in 2019. It is listed on the CKLA website, under research. The study looks at the effect of providing background knowledge instruction. I put the words meta analysis in quotation marks because it’s not actually a meta-analysis, but rather a literature review, as they do not conduct any statistical analysis. The study claims to have found 32 applicable RCT’s. However, they do not list which studies in their bibliography were part of the 32, nor do they include their inclusion criteria. That being said, they do list the effect sizes found in three individual studies: Cabell 2002, Cabell 2019, and Elleman 2009. Strangely, the Elleman paper is another Meta-Analysis and not an RCT. Moreover the Elleman paper is not CKLA.

Cabell conducted an unpublished study, on an unspecified date, examining the effect of CKLA on kindergarten students. While unpublished, the study found results within the normal range. 

Core Knowledge conducted their own pilot study on grade 5 students in 2019. The CKLA study had a sample size of 5602 grade 5 students and was 1 year long. The study found an ES of .38, which is low moderate. 

Abele, Et al, conducted an unpublished study in 2000, comparing the results of 5 CKLA schools to 5 non CKLA schools. The results of this study were extremely negative. This study looked at 10 different outcomes. In 8 of the 10 outcomes the CKLA schools had worse results than the control schools. Effect sizes for this paper could not be calculated. 

Discussion of Studies Included:

There are some issues of concern with these papers. We have a severe sponsorship bias, with most of the studies being connected to Core Knowledge. Several of the papers excluded non-significant effect sizes, which will bias the results to be higher. Non-standardized tests were used, which likely increased effect sizes. We also have two papers that were supposed to be completed, but never published, which raises the question of whether the “file drawer problem” is inflating these results. That being said, results were typically moderate and not high. 

Results: