Changes in instructional hours in four subjects by public school teachers of grades 1 through 4 (NCES 2007-305)

Morton, B., & Dalton, B. (2007). Changes in instructional hours in four subjects by public school teachers of grades 1 through 4 (NCES 2007-305). National Center for Education Statistics, Institute of Education Sciences, U.S. Department of Education. Washington, DC.