YES, THE TEXTBOOKS will be borrowed, the building a bit worn and the principal temporary, but the academic opportunities for Washington's public schoolchildren from every section of the city will be far brighter than they have been in recent memory when the city's new model high school opens for scholastic business at Georgia Avenue and Euclid Street NW in less than two weeks. As a serious effort to recapture the confidence of parents and children throughout the community, the school cannot help but broaden horizons for many young achievers whose options up to now have been limited.

The immediate danger, of course, is that quick-trigger critics will find and exaggerate any bug in this experiment. The average grades of students who are enrolled fall far short of straight A, for example, but their seriousness of academic purpose may be far more important over the coming report periods. Their preparation for college and jobs may also improve markedly.

While the new school may well attract middle-class students who in the past have been abandoning the public schools for private, parochial or suburban classrooms, the importance of this venture is that it is open to all--and the initial enrollment bears that out: Most of the students will be the young, gifted and black students from Anacostia, far Northeast and far Southeast.

The idea is not to create a threat to existing schools, or to establish a favored school when it comes to financial assistance. On the contrary, what succeeds in this model school can and should spread to other high school classrooms as parents, principals, teachers and children find more ways to attract and stimulate academic achievement.

There are bound to be disappointments, too, as the experiment proceeds. But for now, Washington's model high school deserves all the constructive support a concerned community can muster.