About 270,000 new students, a comparative handful in a country of nearly a billion people, began studying at Chinese universities this week, the highest scoring and youngest class yet in China's new campaign to revive a technical elite.

Last week, disturbed students gathered outside Peking municipal headquarters to complain about being passed over by universities despite good scores on the college entrance exam, a measure of the importance of the youthful elite and the complaints about the new system now surfacing for the first time.

"Nobody knows how hard we worked to prepare for the examination, working in summer heat and when we were ill," said a Peking wallposter. "What is the reason for our rejection?"

"I got a 320, and 320 was the cutoff, but nobody will tell me why I didn't get in," complained Li Min, 20, as he and about a hundred other students exchanged experiences near the government office.

It has been two years since the national entrance examination was restored after more than a decade in which political fervor and connections decided most college admissions.

Most Chinese citizens questioned now applaud the change to the merit exam, but it raises new problems in a society already overburdened by grievances against the bureaucracy and uncertain how to pursue its Marxist commitment to rule by the working class.

New figures released by the New China News Agency suggest that the peasants and workers, who represent at least 90 percent of China's population, are still experiencing real difficulty getting their children into college.

Among freshmen at Peking University, generally considered China's most prestigious college, only 34 percent were from families of peasants and workers.

Until 1977, students were usually required to spend at least two years working on a farm, a factory or in the Army before applying for university. Many students have been forced to stay in the countryside much longer than that and have found it difficult to prepare for the exams after so much time away from school.

Figures released by the Chinese news agency appeared to confirm the trend toward admitting more students immediately after graduation from the Chinese equivalent of high school.

The agency said 67,000 of the freshmen enrolled at top-level institutions, called key schools, which have first call on the best instructors and equipment. The average age of those newly admitted to the key schools "is under 20, a bit lower than last year," the agency said. "The average age at the Chinese Science and Technology University is only 16.9."

The key school system presents a dilemma for youths taking the two- or three-day exams in mid-summer. They may list only three choices for university, before they know their score on the exam. If they ask to go to Peking University, but have scores good enough only for a minor teachers college, they may not be accepted at any school.

Unlike American high school students, Chinese students are not allowed to apply directly to several different universities at the same time. They are supposed to list their choices and let the government departments responsible handle their application.

Many students whose families have friends or relatives in some universities have been able to short-circuit this process. A Peking wall poster complained that "many people slipped into university through the back door."

The entrance examination has a total of 500 points. The highest score of any freshman this year was 454, the Chinese agency said, made by Ying Zhigiang of Shanghai, now a freshman at Peking University.