Getting rid of remedial courses at colleges and universities could prevent many low-income and minority students from setting foot on campus, a report by a higher education group said. About 13% of all undergraduates--1.6 million students--took at least one remedial course in the 1992-93 school year, according to the report being released today by the American Council on Education. The report said these students often hail from lower-income families, were born outside the United States and do not speak English at home. Nineteen percent of all black, Latino and Asian American undergraduates and 15% of American Indian students took remedial courses in the 1992-93 school year, the report said. That compares with 11% for white undergraduates.