A few decades ago, kindergarteners may have chanted “one, two, buckle my shoe” as the sum total of their counting skills. With Common Core State Standards, they learn not only to add one plus one, but they have to explain why one plus one equals two. In Charlotte-Mecklenburg (N.C.) Schools, educators have leapt into the Common Core with both feet, creating an internal website for teachers to share performance tasks and implementing systemwide, school-based professional learning that has put the standards into practice and tested students on them in the 2012-13 school year. “I came at this with excitement, not, ‘Here’s another initiative rolling out that we have to embrace,’ ” said Ann Clark, deputy superintendent of the district. “Memorizing that one plus one is two