Enroll in a local college using concurrent enrollment if you still attend high school and want to accelerate your education. This allows you to take some college courses while you're still in high school, before receiving your diploma. Some high schools accept college credits. This might automatically pass you out of a class or give you credit for one you haven't taken.
Pass your General Educational Development, or GED, exams. This option is available to high school students, home-schooled students, alternative students and nontraditional students. Study for your exams, take a series of tests, pass them and get your high school equivalency diploma. Getting your GED qualifies you to enroll in most two- and four-year colleges.
Contact your local community college and present your life experience and desire for continuing your education. According to the to the Greater San Jose Alternative Education Collaborative, community colleges in California can accept your enrollment as long as you are 18 years old or older. You don't have to have a high school diploma to get your two-year degree, at least if you live in California. Many community colleges in other states offer programs similar to this, but some of them require you to pass GED coursework through the college before being accepted into a two-year program.
Search on the Internet for online colleges. University of Phoenix allows enrollment into its undergraduate programs if you have your high school diploma, GED, California High School Proficiency Examination certificate or foreign secondary school equivalent. Kaplan University considers applicants who earned their GED.