Washington State study on school library impact

A recent study in the state of Washington showed the wisdom of investing in school librarians. As part of the study, Elizabeth Coker performed a data analysisof a 40-question survey conducted by the Washington State Office of the Superintendent of Public Instruction among 1,486 of the 2,428 K–12 schools in the state. The results  showed that students attending schools with certified teacher-librarians perform better on standardized tests and are more likely to graduate. The reason is that certified teacher-librarians “are far more likely to be directly involved in teaching curriculum-designed around Common Core standards.”
Coker, El (2015). Certified teacher librarians, library quality and student achievement in Washington State public schools. Olympia, WA: Washington Library Media Association. 
https://wala.memberclicks.net/assets/WLMA/Advocacy/wslitreport_final%204_11_15final.pdf