A sample research observation measure and its preparation into a written observer training package for use in evaluating children within or across classrooms is described. The Planned Activity Check (PLA-Check) measure, a time-sample observation of children's participation is planned activities; was used. A training manual based upon the PLA-Check was devised and then revised on the basis of a series of user tests. The use of the PLA-Check training manual was found to be sufficient as an exportable training program for observers on the use of a standardized measurement system of classroom participation. The study also provides an example of procedures useful in developing a measure for general use. Last, the PLA-Check as a measure provides an evaluation process for across setting comparison of classrooms and techniques. Tables and graphs are included in the study to show the reliability of the observer at different phases of development. (MP)