10th grader wants to graduate high school early

I did this! I became an exchange student in what would have been my senior year. However, this was obviously an earlier era. The school, with mutual agreement, had me graduate with my normal class, and didn't pester me about funding. OUSD shouldn't be able to control your child in that way, and I wonder if a consult with a lawyer would help. It could be worthwhile - if your child feels ready for the next step of life, s/he should be allowed without penalty. How does OUSD handle exchange student requests? Maybe consider that option - it would be bad publicity if they refused to credit students wanting to study abroad.  

If you don’t care about your kid graduating specifically from OUSD, you can transfer your child to your own private school of one student. It is totally legal to establish your own private school. The only trick is you will be responsible for all of the grades, records, and everything else. (There are plenty of resources to help you do this!) You have to fill out a “private school affidavit” form with the state: https://www3.cde.ca.gov/psa

There are lots of homeschooling resources with information about this type of situation. For example, you might contact the Bay Area Gifted Homeschoolers Group, as they have plenty of kids who graduate early, or are “dual enrolled” both high school and college classes: https://www.sfbaghs.org

The homeschooling community in the Bay Area is large and well-developed, and they are typically very helpful with information. You could also maybe transfer your kid to a school system that has a homeschooling arm, like Connecting Waters Charter School out in Waterford Township. (These types of schools require you be residents of their specific county.) 

You do have options. You just have to dig around and ask parents who’ve chosen an alternate educational path for their kid/s. They will likely help you out! 

You can register as a Private School and graduate your child or, instead of early graduation, keep them "in school" and take community college classes for free.  My PSA kids take community college classes online from schools int eh bay area as well as So Cal.  Yes, your child will still get into 4y colleges, if that is their goal, from SLACs to UCs and Ivys. Please reach out to the great volunteer run organization HSC for all your questions.  They have a great help line!  1-888-HSC-4440  https://www.hsc.org/filing-a-psa 

After completing 10th grade your student can take the CHSPE and effectively test-out of high school. No graduation ceremony, but it is the equivalent of high school. My kiddo did this when they were derailed by Covid and zoom. 
 

Everything you need to create your own private school in order to graduate a student early in California is at HSC.org/quickguide and you can also call the phone line to get immediate advice and help at 888-HSC-4440 on how to pull your child and graduate them. No GED/CHSPE (now called CPP) needed, you’ll issue a diploma from your school as the administrator. Depending on future goals, HSC can give advice on the best way to proceed (college, etc). It’s very do-able. 

They can finish HS at a community college and get a HS diploma from the college.

What is your goal? To start college early? Take a year off? Just get out of dodge? What are their college goals? -- The answers to those questions will heavily influence your options. 

We have friends whose teen went the CHSPE route and then took classes at community college before applying to UC as a transfer student. I have no idea how private colleges look at this, but the UC transfer process for a strong student was straightforward. You can also definitely look at both https://www.connectionsacademy.com/california-online-school/ and the homeschooling resources shared here. 

That said, when I read your question my initial thought was that you're not asking the right people the right questions. The graduation requirements listed at https://www.ousd.org/high-school-linked-learning-office/for-students-families/hs-graduation-requirements are pretty unambiguous. You and your child should be able to meet with their guidance counselor and discuss their options for completing those requirements early.  I suggest reaching out to their academic counselor and being specific about what you want. "My understanding is that by the conclusion of semester X, my child will have completed the necessary credits for graduation. We would like to understand the process for early graduation." I would include a rundown  that shows that you're taking into account not just the total credits but OUSD's a-g requirements as well.

There are a lot of local families in GHA who have their kids in community college classes. Join and learn how to keep you kid engaged. https://www.giftedhomeschoolalliance.org/