Some school districts have quietly adopted regulations that permit students who are legally adults to sign for their own absences and off-camous passes. The threshold issue is to determine the rules applicable to you. If your school will not allow this and you wish to pursue this, meet with the school principal to discuss an individual waiver of the rule in your favor. Don't just act on your own interpretation or you will cause the school to be very invested in a formal and harsh reaction (to set an example and hold the line).
If you have a Legal Guardian your status may not be that of a full adult responsible for self, even if the law would allow you that status but for the guardian. That can be a technical issue with some room for interpretation. See a local attorney for analysis of that issue.
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Most likely you can. Each state may set its age of majority in CA, Prior to March 4, 1972, the age of majority in California was 21. California lowered its age of majority after the passage of the 26th Amendment to the U.S. Constitution in 1971, which lowered the legal voting age to 18. As of October 2010, the age of majority is identified by California Family Code Section 6501. The law defines an adult as an individual who is at least 18 years old.
All legal rights vest in you unless a court of competent jurisdiction has vested certain powers or your decision making authority (powers), to someone else such as a conservator since your over the age of 18. The issue you may have is whether you truly have legal guardians any longer. If so and what the court has done as far as issuing orders. I suggest you ask them for a copy of the orders granting guardianship. Welcome to adulthood. Pick your battles carefully. The flip side---Guardians may no longer be responsible for providing for your needs.
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