Some people call it the Summer Melt: It's the tendency for children to get out of the practice of learning over the summertime. Experts say a wide range of activities ward off the Melt — activities that more affluent families often provide children through summer camps and other programs.

There’s an effort underway in Boston to give inner-city children some of those same experiences.

Mark Osario grits his teeth as he pulls on a rope and a sail above him unfurls.

The 10-year-old is in a sailboat about the size of a big car. A heavy metal pole swings over his head and a nearby friend shouts at him.

“Mark watch out!”

“I know," Osario replied. "One-two-three, pull!”

Osario had never been in a boat until two summers ago, when he started sailing with the nonprofit group Courageous Sailing. He’s learned to enjoy afternoons on the water.

“Especially on rainy days and windy days," he said. "When you tip over it’s fun.”

But at lunch, in nearby Charlestown’s Harvard Kent Elementary School, Osario says he doesn’t know if he’ll keep sailing.

“If I have the chance to do it, I’ll do it," he said. "I might have a chance."

And he might not. This program — the Summer Learning Project — is set to run out of money this year. It combines some traditional academic classes with activities that are usually only available to affluent or suburban kids. The program has 10 sites across the city where inner-city Boston children are swimming in the ocean, hiking on an island, or learning archery.

“There are kids that have more opportunities for experiences," said Diane Gould, who runs the program site at Harvard-Kent. "This whole project — we wanted to give more kids that opportunity for better experience. It didn’t matter if they were rich or poor.”

The New York-based Wallace Foundation paid for most of this — $3 million over three years — as part of a first-of-its kind study. Researchers are tracking if students in the summer learning project improve academically during the school year.

Third graders were chosen for the project through a lottery. First they had to turn in a completed application. They couldn’t already be going to summer school for remedial work. Nearly 600 kids were selected. Ten-year-old Mattie Gross was happy when she learned she was one of them.

“But then I also felt bad for my other friends, 'cause they wanted to go, bad, but they couldn’t,” she said.

'I'd like everyone to have an opportunity to come here. Because it's not fair for some of us to come here and the other ones stay home, like, do nothing.'

The 400 kids who turned in applications, but weren’t chosen in the lottery, became the “control group.” Researchers are also tracking their academic performance and using that as a comparison to the kids who get to do the sailing and hiking in the Summer Learning Project. The control group got scholarships to go to normal summer programs run by places like the Boys and Girls Clubs of America.

And even though they didn’t get into the Summer Learning Project, the kids in the control group are still lucky because they got into some kind of free district summer program. Right now only 20 percent of the district’s 57,000 students are placed in district summer programs.

Mark Cruz says he would’ve spent the summer inside, playing video games, if he hadn’t been for the Summer Learning Project.

“I’d like everyone to have an opportunity to come here," Cruz said. "Because it’s not fair for some of us to come here and the other ones stay home, like, do nothing."

Cruz says the opportunity to go sailing is worth the time he has to spend in classes.

The classes are in classrooms that are packed up for the summer — with tarps on the walls and chairs stacked in the corner. But those classes also give the kids a lot of individual attention. In this classroom, there are only eight children. They’re learning about things that tie in to their fun activities — like some simple physics involved in the motion of a boat.

Still, Gould can’t predict what the Wallace Foundation will find when it starts compiling all the data on the students academic performance this year.

“It doesn’t always show in the numbers of the academics consistently, but at the same time you see their personalities are expanding, their whole development is growing — socially, emotionally,” Gould said.

It would help Boston Public Schools if kids in the Summer Learning Project showed dramatic academic improvement, because it’s looking for funding to continue the program.

“We actually have been having continuous conversations for months now thinking about ways in which the partner organizations, the funders and the district can continue this program," said Arianna Milotis, who organizes summer learning for BPS. "It’s the consensus that it would be a travesty if the Summer Learning Project went away."

Walking back out to the pier, Milotis says this is the type of summer experience all kids should have.

“People have this negative, you know, 1950s perspective of, ‘summer school’s for punishment,’" she said. "And to us, summer school’s for opportunities. It’s summer enrichment, it’s summer support."

So as 10-year-old Osario prepares for another afternoon of sailing, he says he knows he has to do really well this coming school year so more urban kids like him can have suburban experiences.

“It’s going to be fun today,” he said.