For short periods of recreational study, a Visitor (B) visa can be used
Enrollment in a short recreational course of study, which is not for credit toward a degree or academic certificate, is permitted on a visitor (B) visa. Learn more about Visitor Visas.
Study leading to a U.S. conferred degree or certificate is not permitted on a visitor (B) visa, even if it is for a short duration. For example, distance learning which requires a period of time on the institution’s U.S. campus requires an F-1 visa.