We also live in the Mission district and just had a kid. We love the walkability but are not sure about staying here long term. Obviously house prices are a factor, but I also know people ferrying their kids across the city to school (as school allocation is not based on location in SF) and that sounds completely hellish to me.
This is technically true, but in practice it's up to the parents. If they want to send their kid to their local 'Attendance Area' school, then they can put it as their first choice, and there's a high chance they'll get it.
Most parents who need to drive their kids across the city are doing it because the alternative (their kid goes to the nearest school) is, in some way, worse.
