This article is from the FAQ, by with numerous contributions by others.
Yes. Dependents of A, G, H, L, E, and I aliens may study on a full- or
Workers in the B-2, H-1, H-2, H-3, L-1, E-1 or E-2 categories can pursue
incidental educational activities as long as the educational activity is not
the aliens primary activity.
Note, however, all categories stated above are NOT necessarily permitted
to obtain assistantship type benefits from school.