If you are in the United States as a tourist, on a business trip, or on any other type of nonimmigrant visa and you have decided that you would like to attend a college, school or a language school in the United States, you can request the USCIS to change your status to that of a student while remaining in the United States.
In order to do so, you first need to find an educational institution (college, university, high school) that will accept you as a student. Once you are admitted, the educational institution will issue you a student form called Certificate of Eligibility for Nonimmigrant Student Status. Most commonly this will be a student form I-20.
You then need to submit to the USCIS, application to change your status, Form I-539, along with all supporting evidence such as your I-20, passport and visa pages, Form I-94 and proof that you will be able to pay for your school and living expenses. You will also need to pay a filing fee.
Please note that due to recent changes in law, you must also remain in valid status. It means that if you are in the United States, let’s say on a B-2 tourist visa, you will need to submit another Form I-539, Request to Extend Status. Because USCIS is taking about a year to process change of status requests, you may need to submit 2 or even 3 Extension of Status applications. You can extend your status for a maximum of 6 months on a filed application which is why multiple applications may have to be filed.
Be cautious if you decided to change your status. It is a very time sensitive matter and if you failed to timely file such requests, you will run out of status and become an illegal immigrant.
Things will get trickier if you are on other types of visas. For instance, if you are a work-and-travel J-1 visa student, you cannot extend your J visa. Therefore, you have to be strategic and knowledgeable about how to proceed.