You must obtain a student visa to enter the US for academic purposes. The specific type you will need depends on the nature of your studies. You may qualify as an exchange visitor, in which case you will require different documentation. For example, students going to the United States for a semester or more will be treated differently than people in summer travel and au pair programs. Consult a lawyer to be sure of your qualifications.
In order to be eligible for a student visa, you must be going to a school that has been approved by the Student & Exchange Visitor Program (SEVP). Upon acceptance into your school, you will receive automatic enrollment into the Student & Exchange Visitor Information System (SEVIS). You will need to fill out and submit the forms that will be given to you by the school you will be attending. The SEVIS fee for most students is $200 and is $180 for exchange visitors.
Certain students may be eligible to travel to the United States with a visitor (B) visa. There is a program that makes it easier for the citizens of certain countries to enter if they are staying for less than 90 days for recreational study.