PRACTICALLY everyone now seems to agree that high school textbooks are an uninspired, muddled, "dumbed-down" mess. That's the easy part. The hard part is the question of what the books actually should be teaching -- there's anything but universal agreement there. A new report released by the American Federation of Teachers, "Democracy's Untold Story: What World History Texts Neglect," helps sort out the possible answers. It addresses the questions with intelligence and imagination -- and without the ideological agendas that tend to clog this subject.

The report is part of an AFT-supported project called Education for Democracy, whose statement of principles bears the signatures of an array of public figures from Norman Lear to Norman Podhoretz. It proposes that schools abandon the doomed effort to "cover everything" in high school history and instead concentrate on the history of democracy: its development from Judeo-Christian and Greco-Roman principles, its variations and major thinkers, its conflicts with and defeats by other societies and other concepts of government.

To the criticism that this is a back-door route to indoctrination, author Paul Gagnon responds by setting forth the ways to present such a curriculum with rigor and balance: filling texts with excerpts from the great political theorists, requiring students to argue for and against opposing systems, stressing the shortfalls of democracies in practice. A University of Massachusetts professor who has taught both college- and high-school-level history since 1952, Prof. Gagnon wants to see students educated to become committed citizens who understand the value of the institutions passed down to them. He believes that argument and comparative inquiry, rather than one-sided inculcation, constitute the best way of ensuring this result. He would avoid cultural narrowness by having the history-of-democracy theme be "one of several" in the curriculum, noting that ''a junk-free 12-year history curriculum" would allow ample time for the study of other cultures.

The prescription in the new report is subtle and comprehensive and runs some danger of being trivialized or distorted in practice. It poses an enormous, though also probably invigorating, challenge to teachers accustomed to the current ways. As Prof. Gagnon points out, his curriculum would also realistically compel schools to expand their world history requirement from one to two years. Can the textbook establishment shake itself from lethargy enough to approach this degree of reform? It is a worthy challenge for a discipline that has lately been failing to teach a majority of American teen-agers who Churchill and Stalin wer