The Supreme Court agreed yesterday to decide whether a public employe who has the protection of the Constitution when he "blows the whistle" for all to hear loses it when he complains in private to a superior.

The justices will act in a case from Mississippi in which a rural school district in the tense early stages of desegregation in 1971 refused to rehire an admittedly competent black teacher who complained to her principal about practices she claimed to be racially discriminatory.

Federal Judge Irma R. Smith ruled the Western Line Consolidated School District didn't renew Bessie B. Givhan's contract "almost entirely" because it wanted to get rid of an internal "vocal critic." This violated her right of free speech, the judge said.

The 5th U.S. Circuit Court of Appeals reversed the ruling last July in a troubled opinion by Judge Walter P. Gewin that recited the adage that "'hard cases make bad law.' This could be such a case . . ."

"The strong implication" of a series of rulings upholding the right of an individual to speak out publicly "is that private expression by a public employe is not constitutionally protected," Gewin said.

The First Amendment didn't protect Givhan when she complained to principal James Leach, Gewin added, noting that she hadn't tried "to disseminate her view publicly."

"Neither a teacher nor a citizen has a constitutional right to single out a public employe to serve as the audience for his or her privately expressed views, at least in the absence of evidence that the public employe was given that task by law, custom, or school board decision," Gewin wrote.

Circuit Court Judge Paul H. Roney concurred in the ruling but disagreed with the opinion. There are "probably many occasions when First Amendment . . protection will reach private expression by a public employe," he said. But trial judge Smith "erred in casting this case in First Amendment terms," he said.

In petitioning for Supreme Court review, Stephen J. Pollak argued for Givhan that the 5th Circuit ruling "would require a teacher or other public employe to risk his livelihood whenever he makes a reasonable suggestion to his superiors concerning important agency policies or practices."

Pollak also contended that under the 5th Circuit rule "the First Amendment would not prevent a municipal government from revoking a citizen's library privileges or trash collector's services because he complained to an official who the citizen reasonably concluded was the appropriate recipient."