What is the education to become a high school teacher in California?

You need a bachelor's degree and a single subject teaching credential. Most often, students get a bachelor's degree in the subject they want to teach, then get the Single Subject credential in that subject. The Single Subject credential takes a year or more to achieve, and it includes both classes and student teaching. Often, you can get a preliminary credential if you lack a specific class or two, then take those classes within five years to clear your credential. That is a typical timeline, but I also know a teacher who managed to finish both his master's degree and teaching credential within four years, so it is possible.

Bachelor's degree, majoring in the subject you want to teach. Education classes including student teaching. Pass licensing exam in subject you want to teach.

In California or any other US state, you need a four year Bachelor degree in education.