OBJECTIVE: To present data on trends in foods and beverages offered through the National School Lunch Program (NSLP) in public middle and high schools in the years immediately preceding and following implementation of new NSLP standards. METHOD: From 2011 to 2013, primary data collection through the annual Youth, Education, and Society study involved use of mailed questionnaires to obtain data on NSLP meals from schools attended by nationally representative samples of US 8th, 10th, and 12th grade students (N=792 middle schools and 751 high schools). Each school was weighted to represent the percentage of target grade students enrolled, thus allowing analyses examining changes over time in the percentage of students enrolled in (attending) schools with specified NSLP measure outcomes, as well as disparities in NSLP measures based on school characteristics. RESULTS: Significantly more US secondary students attended schools with specified NSLP measures in 2013 than in 2011; increases were observed at both middle and high school levels. Increase rates for some NSLP measures were moderated by school characteristics; where this was the case, moderating associations decreased prior NSLP nutrition environment disparities that were especially evident in smaller schools and schools with higher percentages of minority students. CONCLUSION: Meaningful improvements have been made in the nutritional content of NSLP meals offered to US secondary students; these improvements have reduced prior NSLP meal disparities associated with school characteristics. Schools will need continued help with implementation and compliance monitoring in order to have the best opportunity to improve the nutrition environments for US students.