The Healthy, Hunger-Free Kids Act of 2010 updated the nutrition standards in the National School Lunch and School Breakfast Programs (NSLP and SBP) and expanded universal free meals’ availability in low-income schools. Past studies have shown that school meals are an important resource for children in food-insecure households. This analysis used data from the School Nutrition and Meal Cost Study to classify students as food insecure (FI), marginally secure (MS), or food secure (FS). Diet quality from school and nonschool foods that students consumed was assessed using Healthy Eating Index (HEI)-2010 scores. Chi-squared and two-tailed t-tests were conducted to compare school meal participation, students’ energy intakes, and diet quality across food security groups. FI and MS students were significantly more likely to participate in NSLP than FS students (79%, 71%, and 49%, respectively). SBP participation followed a similar pattern but was lower (38% FI, 33% MS, and 16% FS). Compared to FS students, FI and MS students more likely attended schools offering SBP, universal free meals, or afterschool snacks and suppers. School meals contributed significantly more energy to FI and MS students’ diets than to FS students (22%, 20%, and 13%, respectively). All groups’ dietary intakes from school foods were of higher quality than non-school foods. These findings highlight the role of school meals in meeting the energy and diet quality needs of FI and MS students.