WMF does not have the resources to establish partnerships with
every school district in California, a chapter
would. A chapter also would be able to open up museum doors and get
photographers in.
You might consider making a more general project, one less
Wikipedia-specific, then. There's a lot of good free culture work
beyond Wikipedia and its sister projects, especially here in
California. That would give you a wider potential membership base.
Or you could also do something independent and very schools-focused,
partnering with the Wikimedia Foundation as needed. A more focused
effort like that would be easier to explain to grant-givers, and could
give you a better in with foundations focused on California education.