U.S. CIS recently issued "Special Instructions for B-1/B-2 Visitors Who Want to Enroll in School." In this instructional bulletin, CIS confirms that government regulations,

If someone currently holds B-1 or B-2 status and would like to enroll in classes, it is possible to apply for a change of status to F-1 or M-1 as appropriate if: 1) the individual has not yet enrolled in classes, 2) his/her current status has not expired, and 3) he/she has not engaged in unauthorized employment. Individuals who do not meet these criteria may still be able to apply for an F-1 or M-1 visa at a Consulate outside the U.S.

Click here to see the "Special Instructions."

specifically 8 CFR §214.2(b)(7), prohibit study in the United States while on B-1 or B-2 status. The guidance further states that, before enrolling in classes, individuals who are in B-1 or B-2 status must first acquire F-1 (academic student) or M-1 (vocational student) status. Enrolling in classes while in B-1/B-2 status will result in a status violation. Individuals in B-1 or B-2 status who have violated their nonimmigrant status by enrolling in classes are not eligible to extend their B status or change to F-1 or M-1 status. The regulations provide no exceptions.