STROLL around the country club grounds of the California Institute of Technology on a certain weekday in May and you may become concerned about higher education. Students re-creating the cult film ``Monty Python and the Holy Grail'' trot around campus knocking coconuts together to simulate the sound of horses' hoofs. ``Pirates'' sporting eye patches and bandannas kidnap fair-haired maidens and fly the Jolly Roger from a seized golf cart. Others rappel down the sides of buildings or hack away at the cars they are dismantling on the lush lawns of Caltech. There's even a game of musical chairs on the tree-lined Olive Walk.
Hardly behavior to coax the $11,000-a-year tuition out of a prospective student's parent.
But this is Ditch Day - a time-honored tradition of this respected university, whose campus is usually quieter than an astronomy lab. It's a chance for graduating students to dangle four years of scientific study in the noses of their juniors. And at the college with the highest Scholastic Achievement Test scores in the nation, this is not just a day for typical college pranks.
The tradition began in the 1930s, when Caltech's senior class decided to ``ditch'' school one spring day in favor of the beach. They soon found it necessary to barricade their rooms with stacks of furniture to prevent mischief from underclassmen while they were gone.
Today, Ditch Day at Caltech is a spring rite with a language and etiquette all its own. Underclassmen work to break ``stacks,'' mental puzzles or physical blockades of increasing technological and imaginative complexity, to gain entry to seniors' rooms. Upon entering, they may either wreak havoc on the upperclassman's abode or accept a ``bribe'' (usually food or drinks in the room) to keep the place intact. Once seniors proclaim Ditch Day and leave campus at 8 a.m., they may not return before 5, lest they find themselves - like one unfortunate fellow this year - duct-taped to a tree for the day.
And the ``stacks'' are no longer simple piles of furniture. Seniors devise mind-boggling clues and elaborate mechanical contraptions.
Paul Lee, a junior, worked on a ``stack'' this year that, like many others, resembled a scavenger hunt. Mr. Lee and four fellow students spent most of the day translating clues - left by senior Nicole Vogt - to campus locations where puzzle pieces were hidden. (One such clue, ``soi qui mal y pense,'' was finally recognized as a quotation from Sir Thomas Malory's ``Morte d'Arthur.'' The corresponding puzzle piece was found in a book on Arthur's knights that Ms. Vogt's boyfriend had.)
After collecting the puzzle pieces and working for some time to arrange them correctly, the students read the completed puzzle: ``Speak friend and enter.'' When they typed ``friend'' into the computer keyboard that Vogt had left outside her door, the computer responded in Morse code. The translation told the students to see a woman at the school's physical plant, who promptly gave them the key to Vogt's room. The bribe, says Lee, was ``globs of food.''
Other stacks come with a more technological flavor. Junior Rachel Clark tells of her trials with a computerized poker game - complete with images of players and digitized voices. The game was so good, Ms. Clark sighs, that nobody could beat it.
Leslie McCaffree and friends spent most of the day working feverishly on a stack - only to find that one of their final clues was hidden 350 miles away, at Stanford University. ``It was no problem,'' Leslie says with a laugh. ``We had some friends at Stanford fax it to us.''
Another Caltech favorite is the ``brute-force stack,'' like the one that Sam Dinkin, a freshman, tackled this year. He and several other students worked with an acetylene torch and a healthy dose of elbow grease to dismantle a senior's donated car. The object, Mr. Dinkin explains, was to cram all the parts into four 55-gallon drums. The underclassmen were honor-bound not to enter the senior's unlocked room until the stack was completed.
Some ``techers'' prefer plain silliness. One senior created a ``James Bond stack'' with clues hidden in 007-style videos he'd taped. Another required the underclassmen who chose his stack to create a bad ``Kung Fu'' video - complete with out-of-sync dubbing and obviously faked fight scenes. And it's not unusual for underclassmen to perform embarrassing tasks before entry to a senior's room is granted. Several students last year were required to ``act like a moose'' for 20 minutes.
Ordinarily, Caltech has one of the quietest campuses in America - with plenty of noisy birds but few students in sight. Ditch Day offers an annual release from the quiet intensity of studying here - and a chance to put one's lessons in technology to practical use. In fact, Caltech's brainy students have a history of innovative pranks which dates back at least to the 1920s. More recent legends include constructing a cannon to lob oranges at nearby Pasadena City College and rigging a Rose Bowl scoreboard to show Caltech beating the Massachusetts Institute of Technology. The latest coup was last year's storming of the famous ``HOLLYWOOD'' sign in Los Angeles. By covering certain portions of the letters with dark garbage bags, Caltech students saw their alma mater's name in lights for a day.
With Ditch Day, seniors can plan their own individual tours de force - and they might just make it into the Caltech hall of fame. Some of the best thinkers have even developed scientific problems that eluded Nobel laureates on the school's faculty.
So when do underclassmen start planning their own Ditch Day stacks? A group of first- and second-year students smile mischievously. ``Now,'' they say with a knowing nod. But their lips are all sealed.