Data on how many minutes of instruction were allocated to various aspects of teaching initial addition and subtraction concepts and skills in the Developing Mathematical Processes (DMP) curriculum were summarized for 20 classrooms in grades 1-3. The same curriculum materials were used in each class at each grade level. The number of minutes spent on the 148 specific parts of the curriculum were observed. Each part was then classified in terms of 29 variables (40 codes). From this, data summaries of time spent on each code were prepared for each class. The summary data revealed that each class varied from others in important ways. However, four important features were apparent: (1) classes differed more on total allocated time than in terms of any other characteristic; (2) modification of the curriculum was generally made in all classes to stress practice and skill acquisition and to reduce the time spent on exploration and discussion of mathematical ideas; (3) if students were judged to be "poor," then even more practice and less exploration were given; (4) if students were judged to be "good," then in addition they were given opportunity to explore and discuss ideas. (Author/MNS)