Take your child to the San Francisco Symphony Youth Orchestra on May 15 (and several other symphony programs through July) and get a free child's ticket for each adult ticket purchased. There are 200 tickets available for each of these performances, and they're recommended for kids ages 12+. Kids can be 18 and under to take advantage, and upcoming programs include Beethoven, Bartok, jazz with Mark Inouye and Russian favorites.
To get tickets: call the box office at (415) 864-6000. These tickets aren't available online.