Results of the Behavior Assessment System for Children (BASC) Student Observation Scale (SOS), a measure of classroom behavior, were correlated with results of the BASC Teacher Rating Scale (TRS). Two classroom observations were made of each of 30 students (21 males and 9 females) aged 5 to 11 years. Teachers of those students completed the TRS. Correlations were computed by comparing scales on the TRS with the SOS scales. Selected TRS items were also compared to SOS scales. The stability of the SOS was determined by correlating the two observations with each other. Eleven of the 14 TRS subscales were validated by low to moderate correlations with SOS subscales. Furthermore, all of the selected TRS items correlated significantly with the SOS Adaptive and Maladaptive Totals. These results provide a stringent test of the validity of the TRS. Three tables present study data, and 36 references are included. (Author/SLD)