Complex sentence: A 2013 report concluded that Carnegie Learning Curricula and Cognitive Tutor ® was found to have mixed effects on mathematics achievement for high school students, and a 2009 report claimed that Cognitive Tutor ® Algebra I was found to have potentially positive effects on math achievement.
Split into simpler sentences: A 2013 report concluded that Carnegie Learning Curricula and Cognitive Tutor ® was found to have mixed effects on mathematics achievement for high school students. Yet a 2009 report claimed that Cognitive Tutor ® Algebra I was found to have potentially positive effects on math achievement.