San Francisco, population 865,000, has roughly the same number of dogs as children: 120,000. In many areas of the city, pet grooming shops seem more common than schools.
There is also this: San Francisco’s public school system has around 53,000 students, a sharp drop from 90,000 in 1970.
I reside in SF and while empirically this seems to be true, I'm not sure if the data holds up as revealed by this Medium response. On the other hand, some of the highest rent prices in the nation and small apartments makes it more likely that families would want to move to more suburban areas that are still close enough to the city, like Berkeley, Fremont, Palo Alto, Cupertino, etc.