Some education reformers evidently need to become acquainted with a few facts of life.

One such fact is that there are sharp limits to how many more tasks this nation's schools can be expected to perform, just as there are limits to the taxpayers' willingness and ability to foot the bill for new programs. Still another key fact is that not all learning takes place within the confines of the classroom.These comments are prompted by this week's report from the National Endowment for the Arts, which complains that many students are being left culturally illiterate because American schools are neglecting arts education.

To remedy this situation, the federal arts agency recommends that high schools require students to complete two years of arts instruction.

Up to a point, it's hard to fault the report for wanting the schools to put more emphasis on the arts. After all, people need more than food and shelter; they also need the beauty and regeneration that art can provide. Moreover, as technological and economic advances give Americans more leisure time, a knowledge and appreciation of the arts can help put that time to constructive use.

Even so, the National Endowment's indictment of America's supposed cultural illiteracy is far too sweeping. It ignores the immense growth in public enthusiasm for the arts that has already taken place.

More Americans attend ballet and modern dance performances than attend National Football League games. Untold millions are drawn to opera, symphony concerts, and the theater. Museum attendance in the United States reached 500 million visits in 1977 and has kept climbing.

What's more, the cultural explosion has not been limited just to the biggest cities. In less than two decades, more than 100 performing arts complexes, capable of seating 250,000 people, have been built around the country. Many arts groups have lengthened their seasons and added performances in parks. In fact, Editorial Research Reports notes that "Arts institutions have been struggling to meet the rising demand."

This situation clearly indicates that Americans must be doing something right when it comes to taking an interest in the arts. If that interest really must be stimulated, can't be it accomplished without imposing extra tasks on our already hard-working schools?