In most U.S. states, you can't legally drop out of school until you're 16, and even then, there are often restrictions and requirements you must meet before you can do so. While you're 16, you're close to the age where it might be permissible, but you'll likely need parental consent and may need to demonstrate you have a plan for your education or employment afterward (like enrolling in a GED program or securing a job). The specific rules vary significantly by state.
You should contact your school counselor or a guidance counselor to discuss your options. They can provide you with the specific laws and procedures in your state and help you explore alternatives if dropping out isn't the best path for you.