It is usually offered through community colleges. Not all people enter nursing studies directly from high school. Today's students often enter nursing later in life, have degrees in other fields or are changing careers. Many can only attend college part-time. For this reason, many nursing schools offer joint degree or ladder programs, or credit for relevant experience.
Flexible scheduling is also more common.
Check with your nursing school for exact requirements. Continuing education to maintain competency throughout the career is recommended, and required in some states. Note that some specialty areas require additional experience, study or certification. The rapid changes in our nation's health care system also mean changes in nursing. Some traditional areas of nursing are currently cutting back, while new opportunities arise in others.