The answer may not be as simple as you think. You need to study hard for at least four years after high school, but then there are other factors involved too.
To be admitted to law school, you will need to pass the exams. Then, you'll continue to study law for two more years.
After this, you will graduate from law school. Then, you will return to college to complete the bar exam. You will now be a licensed attorney after passing the exam.