Music: Private music lessons cost $30 per half hour on average, so the Golden Gate Philharmonic Youth orchestra quickly amortizes at $575 to $825 per year. The program is suited for kids of all levels, and the fee includes everything from weekly practices to a weekend sleepaway camp in the redwoods. 555 Portola Dr., 415-863-2676
Tennis: You could spend more on a racket than on the affordable Youth Tennis Advantage program. Just $25 a year buys you lessons at John McLaren Park and Lloyd B. Scott Tennis Court, Monday through Friday, 4 to 6 p.m. Mansell St. (At Visitacion Ave.); 195 Kiska Rd., 415-362-2700
Swimming: Instead of paying around $100 a month for weekly swim lessons, plus a membership fee, opt for the University of San Francisco’s pool. Four half-hour classes for parents and their babies or toddlers cost $55, while an eight-class series for 5- to 11-year- olds costs $120. Turk St. (At Stanyan St.), 415-422-6247
Science: On Monday afternoons between 3:30 and 5:30 p.m., kids can drop in to Excelsior Science Workshop to play around with scraps of wood and plastic, microscopes, pendulums, animal bones, and other interesting stuff—all for free. 35 San Juan Ave., 415-594-9165
Geekery: At Mission Bit, software engineers from big-name tech companies like Facebook and Adobe teach programming classes that are free for students in public middle and high schools. Even cooler: Graduates can land internships at places like Airbnb and Pinterest.
Writing: Local writer Dave Eggers’s nonprofit, 826 Valencia, famously serves as both a pirate paraphernalia store and an after-school tutoring program. On Sundays, anyone between the ages of 6 and 18 can stop by for free help with writing projects, from poetry to English papers. 826 Valencia St., 415-642-5905
Originally published in the November issue of San Francisco