What are the key School Nutition issues

Fast food is the major issue. Here's a very interesting program
initiated by Alice Waters of the world famous Chez Panisse Restaurant
and Café.

http://www.edibleschoolyard.org/homepage.html
The Edible Schoolyard

The Edible Schoolyard, in collaboration with Martin Luther King Junior
Middle School, engages 950 public school students in a one-acre
organic garden and a kitchen classroom. Using food as a unifying
concept, students learn how to grow, harvest, and prepare nutritious
seasonal produce. Experiences in the kitchen and garden foster a
better understanding of how the natural world sustains us, and promote
the environmental and social well being of our school community.

czh-ga made a lovely answer. Another answer is that President Reagan
briefly considered defining ketchup as a vegetable vis-a-vis
federally-funded public-school lunches.

School nutrition nowadays means getting all the junk food out of both
the cafeteria and the vending machines, or more simply, making sure
fatty sugary foods don't show up in our schools.