It doesn't look like much from the street it turns its back to in Northwest Washington, but at the end of the road there's a punchy surprise. The new high school of the Georgetown Day School, besides being a splendid facility for its 400 fortunate students, is a hard, invigorating addition to area architecture.

In form it's your basic, no-nonsense box, but in spirit it's a building that unashamedly wants to be remembered, an economy package wrapped in patterned masonry. The pattern is a weave of square bricks, tan with white intervals, that begins at the base of the building along 42nd Street NW -- unmistakably its rear end -- and continues along the sides before erupting with optical pop on the bowed front fac ade.

How the back of the building got to be placed at the front of the site (actually, one of two "fronts") is a tale involving an odd-shaped lot and the likes and dislikes of nearby residents. There is something to be said for the arrangement -- it's an efficient utilization of limited space and it gives the school and its green playing field a sheltered, campuslike feel.

On the other hand, this is a rude way to treat a street, even one so crummy as the 4700 block of 42nd (the immediate context is a car sales lot and a Safeway store -- a dumb box and then some -- that also turns a brick rear wall to the city). The school is bordered on the north by Davenport Street, which is nothingbut a spur leading to a turnaround and parking for both the school and the Safeway. It is fenced off on the south and northwest from the rear yards of single-family homes along Chesapeake and Ellicott streets, and it's protected from River Road on the southwest (the other "front") by earth berms and planting.

Thus the school is effectively sealed off from the surrounding neighborhood. The message to students is "Stay inside." To the rest of us, it's "Keep out." This is not how it should be in the ideal world or the real one; schools, even private schools drawing students from all over as this one does, should and can be symbols of a community and functioning parts of it.

Architect Philip Esocoff, of Keyes Condon Florance, explains that important aspects of the original plan, all dealing with the related issues of image and connections to the city, were scuttled for reasons of cost, red tape or neighborhood opposition. There was to be a terrace at the back of the building facing 42nd Street that would have transformed a fire door and stairwell into a space for activity. There were to be pylons flanking the Davenport Street spur to establish a visible entryway, a much-needed symbol of transition from city to campus. And there was to be a formal, tree-lined walkway through to River Road, which would have done much to reduce the school's isolation.

Ideas such as these, unfortunately, often are treated as frills; they also tend to stay put once they hit the cutting-room floor. But because none of these proposals is structural, or extraordinarily costly, the potential at least exists for their revival. For its own good and ours, the school should seriously consider constructing the pylon-entry; neighbors should press for the walkway from River Road, which would make, among other things, a terrific shortcut to the Safeway store.

There are other defects. The parking lot, though tidily tucked away in a corner of the site, may prove insufficient when school opens next week. And, curiously, this is a school with no visible name. Nancy Epstein of Keyes Condon Florance says there's a plan to put up a little plaque, but that seems small-minded. I can't comprehend why Georgetown Day School isn't prouder of its name, nor why the architects, having decided to make an ornamental pattern the chief exterior mark of a building, did not make the name an integral part of the pattern.

But basically this is a fine building. The front, once one gets to it, works splendidly. The broad, ceremonial bay with its formal 2-2-3-2-2 rhythm of windows, the asymmetrically placed entrance and the adjacent, narrow, windowless tower make a pleasing composition for which the curvilinear terrace and cascading stairwell form a welcoming cup. The view of the athletic field from the terrace, or for that matter from the main communal rooms (student lounge, library) directly behind the bow in the fac ade, is comforting. Grounds and building together form a simple, cohesive, special place -- a school.

From the outside one supposes right away that the offcenter entranceway is the key to the interior arrangements, and this does turn out to be the case. On each of three floors there is a long east-west corridor separating rows of classrooms on the south from larger, more public spaces (lounge, library, theater, gymnasium, administrative offices) on the north. The facilities are economical but first-rate. Touches of design intelligence abound: a corridor to the art compound doubles as a gallery, the painting studio gets north light through clear glass, interior walls are made of glass block where extra natural light was (correctly) deemed necessary, glass block windows softly illuminate the gym.

Worth special mention is the theater (designed in conjunction with consultant Duane Wilson and built with a grant from the Cafritz Foundation), the idea for which came from an experimental space at the University of Pennsylvania. There's nothing like it in Washington -- it's an exceedingly flexible "black box" (actually painted a deep-night blue), 43 feet high, 40 feet wide, 60 feet long, with catwalks and modular platforms (for performing or seating) but no proscenium and no stage. An advantage that a parent who's attended lots of school performances can appreciate is that student technicians here, working in full view, will share the glory with the bit players and the stars.

From the public point of view, however, the best thing about this building is that decisive patterning of the main fac ade -- it makes something special out of nothing much. It's not surprising to learn that Esocoff went to architecture school at Penn at a time when the spirit of Robert Venturi was pervasive there. The new Georgetown Day School building is what Venturi years ago defined as a "decorated shed." The aluminum-frame, single-hung windows are the kind that Venturi, in "Learning From Las Vegas," termed "ugly and ordinary" (as opposed to the "heroic and original" openings of modernist architecture).

Esocoff's building is not ingratiating, nor afraid to exhibit its economies, its conventional forms and materials. And yet it is not entirely a conventional statement: Those catalogue-order windows are pushed out front with pride, with almost poignant contemporaneity, as if to say, well, this isn't Palazzo Strozzi or the west wall of Chartres Cathedral, but it's the kind of stuff we mostly do now. There's a certain clear-headed poetry at work here, in the way this building transcends ordinariness even while celebrating it.

The National Trust for Historic Preservation has done it again. In preparation for its annual meeting here next month, the trust devoted the most recent edition of its bimonthly magazine, Historic Preservation, to Washington. The just-released September issue of its monthly publication, Preservation News, likewise concentrates on the Washington area.

This, too, is a job well done, containing the latest word on most of the preservation issues in the city, as well as features and essays. Editor Arnold Berke and free-lance writer Mark Jenkins contribute complementary pieces on a tough subject, defined as follows by Berke: "The easy part of preserving historic downtown Washington -- saving landmarks -- is mostly done. Now comes the hard part -- rescuing the small buildings." Jenkins' prognosis is pessimistic, Berke's is cautiously -- very cautiously -- the reverse.

Preservation News is not sold on newsstands, but single copies can be purchased from the trust (673-4072).