Students at Doherty Middle School in Andover, Mass., choose items from the salad bar in the school cafeteria, June 2012. Among other things, a Senate compromise on school nutrition standards calls for the USDA and the CDC to establish new guidance that would encourage the use of salad bars. Melanie Stetson Freeman/The Christian Science Monitor/Getty hide caption

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A school lunch tray featuring whole wheat tortillas at the School Nutrition Association conference in July 2014. The association is asking Congress to relax the federal school nutrition standards in hopes of attracting more kids back to the school lunch line. Charles Krupa/AP hide caption

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First lady Michelle Obama has been doing a lot of high-fiving with schoolchildren like these in Dallas to promote healthful lifestyles. Now she's diving more deeply into the politics of school lunch. LM Otero/AP hide caption

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