Michael Schoch, Answers questions on Noodle
The policies regarding dropouts and re-enrollment differ from school to school and state to state. Since I don't know where you live, I'll suggest that you use the school finder to find public high schools near you. Once you've done that you can call the schools to learn about their policies. Some schools may let you re-enroll and others may ask you to take continuing education courses.
For help with Finding a School check out the articles and advice on Noodle.
If this isn't specific or helpful enough, feel free to write back with more details about your location and current living situation and I'll get you more resources. Best of luck!