This case study examined parent groups' involvement in school activities and their participation in decision making. Research questions included the following: (1) What is the nature of parent groups in schools? (2) What activities and issues gain parent groups' attention and participation? (3) How do parent groups communicate concerns about school policies and practices? (4) What differences, if any, exist between formal and informal parent groups? Social network theory provided the framework for analysis. Seventeen parents in one K-6 elementary school participated in semistructured interviews. Data were analyzed with analytic induction. Participants' interactions around shared activities created dense networks that supported school activities and influenced school leaders' decision making.