The Underground Grammarian vs. verbal nonsense; The Leaning Tower of Babel and Other Affronts From the Underground Grammarian, by Richard Mitchell. Boston and Toronto: Little, Brown & Co. 279 pp. $14.95.

Richard Mitchell is a very perceptive, very funny man. In this, his third collection of essays from his newsletter on education, called the Underground Grammarian, his wit flashes again and again. His targets, now as before, are the professional educators whose occasional pronouncements provide his documentation. Let one example suffice for now, this one taken from a ''pilot curriculum'' for a school district in the West: ''Knowledge represents the lowest level of learning outcomes in the cognitive domain.''

Precisely!

Mitchell traces this ''idea'' back to a publication called ''Taxonomy of Educational Objectives.'' So this little school district is part of a bigger picture after all. Read through Mitchell's book, and it may well seem to be everywhere.

The problem here is not simply that this definition of knowledge is couched in the horrible jargon preferred by ''educationists,'' as Mitchell calls them. The problem is that when you figure out what those poor, tortured vocables are intended to mean, it is something nasty: That is, educationists appear to have forsaken knowledge for the behavioristic sphere (a favorite word among educationists) and the touchy-feely. That is, children are to be trained - not educated, but trained - to relate, to be creative, to be happy.

Knowledge, remember, is the lowest level of learning outcomes. The higher outcomes are subjective and relative. Hear these quotes from educationists (reminiscent, I find, of fragments of dialogue from Joan Didion novels): ''To 'center down' in regard to our children is to me a putting into focus what we are here for.'' And this, from a graduate of a seminar in management at the Stanford Business School: ''We will be looking at the whole scenerio. We are going to start doing an overall look.''

To paraphrase ''Hamlet,'' something is rotten in the overall scenerio anyway. For a while I taught English composition at Mercer County Community College in New Jersey. (Mitchell himself teaches English at Glassboro State in New Jersey.) One morning I found in my box an elaborate memo from the department chair telling me in quantitative terms how to deal with foreign students: ''Studies show'' - you bet they do - ''that interpersonal communications, as they are called, are a function, among other things, of the distance the teacher puts between his body and that of his students. Distance, likewise, is a function of race. The laws governing these functions are expressed in inches.''

It was neat, as Mitchell would say, and I used it as an example of perfect nonsense in class that day, a day when I happened to have a department observer sitting in the back observing.

Richard Mitchell is not a nut. No. He is, besides being right about public education, a great satirist. And like Juvenal, Ben Jonson, and Swift, he has been branded as a case of ill-adjustment. Indeed! For Richard Mitchell lives, as we all in our best moments live, ''under the decent government of vigilant doubt.'' His essays further the work of Orwell, whose essay ''Politics and the English Language'' is discussed here.

Aside from Orwell, Mitchell's heroes include Thomas Jefferson. The final effect Mitchell's book - on the surface the work of a master satirist - has wrought in me is not that of destructive energy. Let me simply say that when I visited the University of Virginia recently I felt it supplied a visual key to what moves Mitchell's pen. Indignation fuels these pieces, yes, but righteous indignation, whose positive side is something akin to the endlessly interesting, elegant, spacious, and happy design of Jefferson's campus. It is a belief that free inquiry, lucid expression, and political and moral freedom are all inseparable. In a sentence worthy of the Great Anthology, Mitchell writes: ''Tyranny is always and everywhere the same, while freedom is always various."

Thomas D'Evelyn is the Monitor's book editor.