This paper provides a detailed empirical account of the performances of 8- to 9-year-olds and 11- to 12-year-olds on a chore-scheduling task developed to assess the dynamics of planning processes. In developing the planning task for revealing different levels of planning proficiency, five critical aspects of planning were taken into account: the need for planning is often not recognized; background knowledge of the situation is necessary for planning; planning is more likely when the situation is complex and novel; planning is a revisionary process; and planning decisions are made at different levels of abstractions. Thirty-two students in a private school in Manhattan were given multiple opportunities to construct the shortest path for accomplishing a series of classroom chores. Careful examination of the processes and products of planning activities across different trials--specifically, think-aloud protocols, strategies for problem solution, and route efficiency--revealed considerable developmental progress within sessions for both younger and older children, and significant age differences; e.g., older children engaged in significantly more higher-level decision making during planning processes. A reference list, the scoring system for featural analysis, and coding categories and definitions for process analysis are included. (Author/THC)