WITH UNANIMITY and wisdom, the D.C. school board has made the first of two decisions this year that will have more to say about the state of public education in Washington than any others the current members are likely to confront. The new board president is Linda Cropp, whose good sense and close personal experience with the D.C. schools make her the best choice to build on the excellent record of her predecessor, R. David Hall. As the board's vice president for the past three years, Mrs. Cropp, whose children are students in the city's schools, has worked closely with Mr. Hall, himself a product of the D.C. system. Along with the new vice president, Wanda Washburn, Mrs. Cropp and Mr. Hall will lead the way to the second critical decision: the choice of a new school superintendent to succeed wonderworker Floretta Dukes McKenzie.

Reports have it that the board has not been exactly swamped by applications, but numbers don't mean much. Back in the hideous adolescence of the elected school board -- when board members all but punched each other out at free-for-all sessions and superintendents didn't know either where they stood or what they stood for -- there were plenty of educationally pedigreed turkeys looking for superintendent work. Some of them got the job too -- and the damage has taken a good decade to undo.

"We have come a long way from the days of instability, negative newspaper headlines and lowered test scores," Mrs. Cropp noted in her first speech as president, praising members and Mrs. McKenzie for creating a more peaceful atmosphere in the classrooms as well as in the board room. But neither Mr. Hall nor Mrs. McKenzie would claim today that the public schools have achieved anything near greatness. While peformances in elementary schools have improved, the high school dropout rate is high, secondary school achievements are not up to par, and parents, teachers and administrators as well as students must cope with the pressures that plague urban schools all around the country. Too many physical plants still are in sorry shape, and too many textbooks and supplies still are slow in coming -- and outdated when they do finally make it.

A good superintendent has to be more than merely an accomplished manager of school systems. The ability to understand and deal with the political structure, to court and sustain the support of business leaders and all the taxpayer-voters who do not have direct interests in the public schools, is essential. There is optimism, and people and organizations do stand ready to sustain that spirit for a skilled and savvy new superintendent -- and that should be of some comfort to the board as it undergoes its difficult initiation.