Although the common-core standards are calibrated to ensure that students leave K-12 schools ready for work and college, they are also posing challenges for the educators who work with children just starting out their school careers. As 46 states and the District of Columbia work this year to put the new curricular guidelines in place, preschool and early-childhood educators are determining how to balance the common standards' emphasis on increasing and measuring academic rigor with research findings on young children's developmental needs, which place a high value on play, the arts, social skills, and integrated instruction. Every state has guidelines outlining what preschool-age children should be able to do in a number of developmental domains, according to a 2007 review of states' policies published in the journal "Early Childhood Research & Practice." But in the 2011-12 school year, fourteen states rolled out the common-core standards for kindergarten, K-1, or K-2, according to Carrie Heath Phillips of the Council of Chief State School Officers, and that puts issues of school readiness and the content of those preschool skill guidelines in the spotlight.