We are proposing an observational study of kindergarten math instruction in the New York City (NYC) public schools during the spring and fall of 2016 which would provide, to our knowledge, the first detailed evidence about the quantity, content and quality of kindergarten mathematics instruction in the United States. In addition, the proposed study will offer critical information about kindergarten mathematics instruction in the first years of full implementation of the Common Core State Standards in Mathematics (CCSSM). The study will be designed to answer the following research questions: How much time do kindergarten teachers spend on math instruction (both formal and informal) relative to other curricular topics? What mathematics content is covered in NYC kindergarten classrooms? What is the quality and depth of the mathematics instruction that occurs in these classrooms? How do kindergarten teachers decide what mathematics content to teach, how they will teach it, and how much instructional time and emphasis to give to mathematics instruction in general and specific mathematics topics in particular. The study will begin in October 2015 and ending in December of 2016. A total of 30 full-day observations (15 in spring 2016 and 15 in fall 2016) in 15 classrooms will be conducted. In addition, we will develop a short semi-structured interview protocol that will be administered to all teachers whose classrooms are observed.