A collaborative day care and public school kindergarten intervention program for children in several public housing projects in Boston was evaluated by means of the Bronson Social and Task Skill Profile, a classroom observation instrument. This instrument has categories that measure behaviors related to competence in carrying out social interactions and mastery tasks. The intervention group, and comparison children from the same classrooms, were observed four times over a 2-year period--in the fall and spring of their pre-kindergarten and kindergarten years. Comparison children came from the same working class neighborhood as those in the intervention group, but had more economic advantages. Almost none were minority group members. Results demonstrated a progressive catch up effect in most observed behavior categories for the intervention group in relation to the comparison sample. Very poor performance by a few children who were eligible for the intervention but did not receive it further underlined the effectiveness of the intervention. The inclusion of both social and mastery categories in the observation instrument proved useful in providing information on areas of skill and weakness in the samples. (Author/RH)