For many students, summer is a time for play, rest or just hanging out.

But this summer some Fresno County students will be part of a research project that's intended to keep them fit, both academically and physically.

The program, offered through the Fresno County Office of Education and located at Central East High School, will enroll 380 Central Unified middle school students in summer school, where they will study English-language arts, science, technology, engineering and math lessons that will reinforce what they were taught earlier this year. They'll also learn about proper nutrition and participate in exercise.

After summer school, they'll be tested to determine how much they've retained.

The program is designed to level the playing field between low-income students and those from wealthier families, who travel or attend camps and tend not to forget as much from the school year, officials said.

"Statistics show that students from a middle-class upbringing have enriching experiences that will allow them to reinforce what they learned during the year so they don't experience the knowledge loss that lower-income kids do," said Alix Frazer, director of after-school programs with the Fresno County Office of Education.

The full-day summer school program will last five to six weeks. It is funded by the Packard Foundation and will be offered in Fresno and seven other California communities -- Oakland, Los Angeles, Santa Ana, San Francisco, Sacramento, Gilroy and Whittier.

Without summer school, many children stay home, watch television and eat junk food, which increases childhood obesity, said Jennifer Peck, executive director with the nonprofit California Partnership for Children and Youth, which is working with the Packard Foundation.

In the summer "children are more often sedentary, in front of a television with video games," Peck said. "Low-income kids are now gaining weight more rapidly during the summer because they lose access to organized physical activity and meal plans."

The new program is much needed: From 2009-10, 65,000 students in California -- about 13% of the state's summer school students -- lost access to nutrition programs at school sites, a California Association of Food Banks study said.