"The United States demands onsite investigations of all chemical and biological weapons sites," said the U.S. delegate. "I now yield the floor to questions."

Fifty more delegates rose to challenge her.

Later these diplomats would be reprimanded for passing obscene notes and making noise, something out of the ordinary at most international gatherings.

But such undiplomatic behavior was all that could be expected from a bunch of high school kids up for the weekend at the 29th annual Harvard Model United Nations, and under the supervision of undergraduates.

At one of the largest debates for secondary school students in the country, the weighty and the flighty seemed to go hand in hand. The budding politicos stay at the Copley Marriott and commute to Harvard for caucuses and debates for the cause of world peace.

They would have stayed at the Sheraton, as in previous years, but that hotel balked at hosting delegates again after widespread student carousing last year, student officials said.

Members of Harvard's International Relations Council are directing approximately 1700 delegates from more than 115 schools in the U.N.--style debates, which began Thursday and conclude tomorrow.

"The object is to learn to discuss rationally," Fiji delegate and erst-while Milton Academy student Joe F. Toot said yesterday. "Our resolutions should offer real solutions to real conflicts," he added.