In what it believes is a fresh approach to attacking school segregation, the Reagan administration plans to sue school boards it believes are providing inferior public education to students in black and Hispanic schools.

"I don't think this is a minor problem or an isolated one," William Bradford Reynolds, assistant attorney general for civil rights at the Justice Department, said in a telephone interview yesterday. "I think it exists in a number of places around the country. This is clearly the direction we're going and we're going to move very energetically in this direction."

He also said the Justice Department may join one or more school districts, which he refused to identify, in asking federal judges to lift existing busing orders. He said the department would require the districts to have magnet schools with special programs, change school boundaries, and offer incentives such as free college tuition for students to transfer to schools where they would be in a racial minority.

In an interview with the Los Angeles Times, Reynolds refused to say when or where the first suits would be filed except to acknowledge that the first one would not be filed immediately and would not be the first of a barrage of lawsuits. Said Reynolds: "I can't begin to send off signals as to where or when or every school board in the country is going to start calling me and asking about it, but I can say this will not be an all-out assault."

The plan to sue school boards on the quality of their education reflects the Reagan administration's approach to school segregation, which is to deemphasize the busing and racial quota approaches to the question. Attorney General William French Smith has often said he does not favor busing or racial quotas as the answers to the question of school segregation.

Reynolds conceded that the new approach is likely to match the federal government against de-facto segregation, which comes from neighborhood housing patterns rather than state neglect. The civil rights chief said this is not a reason to shun these suits.

"Uneven treatment at the education level suggests a different kind of constitutional violation than the one dealing with separateness," Reynolds said. "I think it's just as real a violation and the obligation of this department is not to blink at it."

How will the Justice Department go about deciding which school boards should be sued because they provide an inferior education to their minority students?

"There are some situations that just jump out at you," Reynolds said, "and since most of the litigation we get involved in is based on complaints, those complaints will continue to be the focal point of our investigations."