Common Core impact study

Test scores vary little between states using Common Core State Standards and those not using the standards, according to a recent report Data show Common Core is changing instruction, with 45% of teachers emphasizing nonfiction in 2015, up from 38% in 2011. Principals are most likely to influence instruction by developing and setting educational goals for their schools.
Brown Center on Education Policy. (2016). Brown Center report on American education. Washington, DC: Brookings Institute.
http://www.brookings.edu/research/reports2/2016/03/24-brown-center-report-loveless