Complex sentence: Gardner supported eliminating Washington's WASL test, a standardized test that was required to graduate high school, it was replaced in 2009 by the MSP for grades three through eight and the HSPE for grades eight through twelve.
Split into simpler sentences: Gardner supported eliminating Washington's WASL test, a standardized test that was required to graduate high school. It was replaced in 2009 by the MSP for grades three through eight and the HSPE for grades eight through twelve.