If the plan beneficiary chooses not to go to college, you can change the beneficiary to another family member!
You will need to check if your state tax law would apply a penalty. If you withdraw the assets for non-qualified expenses, the earnings portion, though not the contributions, would be subject to tax plus a penalty.
529 plans are generally used to save for college expenses but they may be used for K-12 tuition without federal tax penalties.
While SoFi does not currently offer a 529 savings plan, we may refer you to options through this 529 College Savings Plan Selection Tool (to access you will need to have a SoFi account).