This study examines the relationship between school meal program participation and diet quality of children over a 24-hour period using data from the third School Nutrition Dietary Assessment Study (SNDA-III). Diet quality was assessed using a slightly modified version of the Healthy Eating Index (HEI-2005) that more precisely reflected recommended food intake patterns for school-age children. The assessment also examined the relative contributions of specific foods to children’s MyPyramid food group intakes. Propensity score matching techniques were used to control for differences in observed characteristics of school meal participants and nonparticipants. Overall, there were no significant differences in diet quality between school meal participants and nonparticipants on total modified HEI-2005 scores. However, National School Lunch Program (NSLP) participation and School Breakfast Program participation were both associated with a significantly higher score on the Milk component of the modified HEI-2005, and NSLP participants scored significantly lower than nonparticipants on the Oils component (this component tracks healthy, recommended oils, so a lower score is a negative outcome).