WASHINGTON, March 29 - The Supreme Court ruled on Tuesday that the federal law barring sex discrimination in schools and colleges also prohibits school officials from retaliating against those who bring sex discrimination complaints.

The 5-to-4 ruling resolved conflicting interpretations in the lower courts over the scope of the law, Title IX of the Education Amendments of 1972.

While the margin was narrow, the language of Justice Sandra Day O'Connor's majority opinion was sweeping. For Title IX's advocates, who have been placed on the defensive in recent years by complaints from critics that the law's obligations are too burdensome, the ruling was a decisive victory.