WASHINGTON — Children placed under foster care system by a state or court are “categorically eligible to receive free meals in all U.S.D.A. child nutrition programs,” the U.S. Department of Agriculture said this week. The expansion is part of the Healthy, Hunger-Free Kids Act of 2010, signed into law by President Obama Dec. 13. Based on data from the federal Adoption and Foster Care Analysis and Reporting System, 423,773 children were in foster care as of September 2009. The new provision of the child nutrition law is aimed at reducing the administrative burdens on states, schools and foster care families by certifying eligible foster children for free meals in the National School Lunch and other child nutrition programs without requiring an application. The National School Lunch Program serves about 32 million children each school day. “Ensuring foster children have access to healthy, balanced and nutritious meals without the burden of unnecessary eligibility paperwork shows our commitment in providing the best quality of life for many deserving children and their families,” said David A. Hansell, acting assistant secretary for children and families at the Department of Health and Human Services. H.H.S. announced the program expansion in cooperation with the U.S.D.A.