Lindsay Wildlife Museum is a unique natural history and environmental education center where live, wild animals are just inches away. More than 50 species of live, non-releasable, native California animals are on exhibit. Located in Walnut Creek in the midst of a residential area, this museum has a grassroots feeling and is small, but also specializes in rehabilitating native California animals in their animal hospital.
Lindsey Wildlife Museum

A great place for field trips, plus personal/teacher time with NightLife and The Naturalist Center. The website itself isn't very fun to navigate.
California Academy of Sciences

I heard about this through a teacher friend on Facebook. They have a lovely goat farm with a shop that's open on weekends. They do school tours, too!
Harley Farms Goat Dairy

This farm is located right in the middle of a ton of public and private schools in Vallejo, CA, as well as youth and rehabilitation programs. Sadly, it is used most by rich preschools from around the Bay Area. Farmer Rita even went so far as to get her Master's in order to link farm curriculum with California learning standards! This place is beautiful.
Open to the public Monday-Friday, 9:00-2:30, this farm is amidst public schools, private schools, and school and community programs:
Loma Vista Farm

Recommended by Bruce H. Tiffney, Dean, College of Creative Studies, University of California, Santa Barbara:
Natural History Museum, Los Angeles County

Recommended by Bruce H. Tiffney, Dean, College of Creative Studies, University of California, Santa Barbara:
San Diego Natural History Museum

Recommended by Bruce H. Tiffney, Dean, College of Creative Studies, University of California, Santa Barbara:
Santa Barbara Musem of Natural History

The Anthropology Department at UC Davis regularly gives presentations to school groups of all ages, and prehistoric technology/flintknapping is one of their most popular topics. They are flexible in arranging dates and times, and public parking is available in some UC Davis lots, with the department located in Young Hall. Departmental volunteers can show students around the archaeology labs, give them a presentation on California archaeology, and do some flintknapping outside. All of their presentations are very hands on, and students would get to see and handle a variety of artifacts. They are pleased to be able to offer presentations completely free of charge to interested students. They request only that, if you and your students enjoy the presentation, you email them a thank you letter including the name of your school, date of visit, and the number of students who attended:
Center for Archaeological Research at Davis