In the summer, some affluent kids shoot hoops at a $69 two-hour basketball session with the Harlem Globetrotters, ride Arabian horses for $525 a week or visit Costa Rica for a $3,500 two-week study of sea turtles.
But many more students are like Christopher Leon-Sanchez, of San Jose, who has never traveled out of state or even attended a summer camp. "It's always been the money," said the James Lick High senior.
The stark contrast between the summer activities of the Bay Area's have and have-not children not only highlights ethnic and class differences but also distinguishes who is likely to succeed -- and who may struggle in school and later in life.
Studies say that what children do in June, July and August dramatically affects their skills, knowledge and capacity to learn. A 2013 Rand Corp. study found wealthier students often gain ground in the summer while low-income students fall back, and that this summer slide is cumulative. "It may be that efforts to close the achievement gap during the school year alone will be unsuccessful," the study said.
Last spring, Leon-Sanchez applied to a summer Stanford University program that appealed to his interest in medicine and would enhance his college resume. But his family couldn't afford the $3,000 price tag.
So instead, the 16-year-old is doing a community-organizing internship and washing dishes in a restaurant.
"In my family, it's all work, work, work," ¿Leon-Sanchez said.
And among his acquaintances, he said, "a good 80 percent are doing absolutely nothing this summer."
Such idleness worries parents. Josefina Ramirez, of San Jose, said that even her neighborhood library is often closed, leaving mothers few options aside from walking in parks, going shopping and occasionally eating at McDonald's. She and her husband would love to take their three children on a trip, but said,"We can't give them the luxury of traveling."
Research shows only one-third of low-income youth participate in any summer learning program.
"There's a huge learning loss," said Gaylynne Hudson, who teaches English learners in Oakland. That's particularly true of immigrant children who don't hear English or have many books in the home. "The listening skills they've learned drop way off. It's really hard for them."
The widespread disappearance in California of summer school for both enrichment and remediation has many worried.
A Johns Hopkins University study in 2007 found two-thirds of the achievement gap between rich and poor ninth-graders is linked to disparities in summer activities -- not just academics, but also sports, travel and camps.
In the Bay Area, public and community programs are striving to narrow the gap.
About 1,000 students boosted their math skills this summer at a free six-week program run by the Santa Clara-based ALearn. The program seeks to prepare low-income sixth- and seventh-graders for algebra and to make sure incoming ninth-graders who struggled with algebra master it during the summer to avoid a remedial class in high school.
Julissa Hernandez, 14, will be heading into geometry at Los Altos High, thanks to ALearn. While she was sad to miss a relaxed summer, she liked her teacher, Jared Darby, 33, an actuary-turned-math-teacher and an expert at engaging students in a subject that many think isn't for them.
"I'm creating an environment that they can be present in," he said. Once he has their attention, he said, students learn.
The summer before freshman year is crucial, ALearn founder Kathryn Hanson said. Thus, ALearn students spend the afternoons preparing for the rigors and culture of high school.
Her children, now grown, attended summer programs like those offered by NASA and Johns Hopkins. "There just wasn't anything for kids whose families didn't have those capabilities. Students need that preparation for real academic work."
Groups like BELL (Building Educated Leaders for Life) aim at younger children. BELL runs a five-week program in various cities that combines academics with fun classes like art, sports and Zumba. It has a long waiting list. "They're typically kids from families who can't afford to send them to the Y," said Naomi Eason, executive director of BELL California.
But with 260 students in San Jose and 120 in Oakland, programs like BELL touch only a small portion of the vast pool of students with limited access to an enriching summer.
Educators long have recognized the value of summer programs, whether exotic or homegrown. Parents, too, see the impact.
Martha Kokes' two daughters have attended a theater camp in Boulder Creek for several summers. The camp is taught by actors working on Broadway, in Hollywood and on tours. The Young Actors' Theatre Camp offers songwriting, Disney dancing, screenwriting, set designing and even personal voice coaching.
"I cannot say enough good things about it," said Kokes, of Burlingame. When her daughters return from camp, "they walk a little taller, they shine a little brighter."
It's the kind of camp many students would love to attend.
Christina Truong, 16, of San Jose, had no summer school options offered by her school district, East Side Union, which referred her to community college. But the textbooks are costly, and she had no transportation to Evergreen College.
With free programs nearly impossible to get in and other programs running up to $6,000, she said, "My family can't handle it."
Contact Sharon Noguchi at 408-271-3775. Follow her at Twitter.com/noguchionk12.