It is possible to apply to change status from tourist to student. Whether it is approved or not depends upon several factors, including how long one was here before applying for the change of status, what s/he told the consular officer at the time of application for the visitor visa, and whether s/he has adequate financial support to attend school. An additional factor that is sometimes raised by the USCIS, but more often by consulates, is whether you one has the ability to show an intention to return to the home country. As a practical matter, you should be aware that a change of status application can take several months (4-8 months at the time of this writing) and, although one may have been accepted into an academic program, s/he is not legally authorized to attend classes until the application has been approved.
Attorneys at Law
