Boston — Colleges and high schools in the United States have stopped saying ''c'est la vie'' to declining foreign-language enrollment. There is evidence to suggest that attitudes toward foreign languages are turning around, but the number of students taking language courses remains low by historical standards. A few statistics gathered from several sources, including US Rep. Paul Simon's book, ''The Tongue-Tied American,'' highlight the problem:
* Less than 1 percent of the 11 million students in undergraduate and graduate studies in American colleges and universities currently studies the foreign languages that are spoken by three-fourths of the world's population; even fewer become fluent in one.
* There are more teachers of English in the Soviet Union than there are students of Russian in the US.
* Only 15 percent of American high school students are studying French, German, or Spanish, and only 1 in 20 of them goes beyond two years of study.
* Only 8 percent of American universities require a foreign language for admission, down from about 85 percent in 1915 and 34 percent as recently as 1966 .
''At a time when it is more important than ever that we communicate with the rest of the world, US citizens are notoriously deficient in foreign-language skills, and statistics suggest they are getting more tongue-tied every day,'' says Representative Simon (D) of Illinois, chairman of the House subcommittee on postsecondary education.
Why is foreign-language competency so vital? Experts see the importance of language study not so much as an academic exercise, but as a means for fostering cross-cultural understanding. Such understanding is sometimes indispensable in the realms of diplomacy, national security, and international business.
A well-known example of the diplomatic problems that can be caused by language deficiency was the lack of Farsi-speaking diplomats at the American Embassy in Tehran during the Iranian revolution. Many observers believe that the failure to foresee or head off the embassy takeover can be traced, at least in part, to inadequate language training.
The US government acknowledges the direct link between national security and foreign-language competency. The supersecret National Security Agency recently invited 15 colleges and universities to take part in a program designed to encourage the study of the Russian language.
Government agencies in particular are beginning to feel the effects of the declining number of experts in Russian and other languages.
In terms of international business, foreign-language incompetence tends to hamper the ability of Americans to operate effectively overseas and puts them in a position of waiting for others to come to them.
''Most of the US firms which should be exporting today are not,'' says Simon, ''and a major reason for that is our inability to speak the language of our customers. We need to learn a fundamental lesson from our Japanese and West German competitors: You can buy in any language, but you cannot sell in any language.''
As concerned as educators are about the decline in foreign-language competency, signs indicate the downward trend is bottoming out. Enrollments are up at some colleges and universities; a number of others have reinstituted language requirements; and efforts are being made to train more teachers in the field.
The resurgence may have been touched off in part by a report issued in 1979 by the President's Commission on Foreign Language and International Studies. It found ''scandalous incompetence'' in the teaching of foreign language in American schools and offered more than 100 specific recommendations to alleviate the problem.
The report ''has boosted some college departments of language,'' says John Rassias, a nationally known professor of language at Dartmouth College in Hanover, N.H., and a member of the commission. ''The turnouts are bigger and bigger, enrollments are increasing. But most of this is individual effort on the part of the colleges.''
Despite the efforts of the education community, Congress remains lukewarm in its support of legislation to upgrade foreign-language instruction in schools. No significant federal legislation followed in the wake of the report.
Congress is considering a $50 million bill, entitled Foreign Language for National Security, which would fund model language programs and provide grants to colleges based on foreign-language enrollment. While similar legislation has been shelved in the past, the chances for passage of this bill are rated as good this session.
A recently passed bill designed to upgrade science and math instruction included scholarship money for those promising to teach ''critical languages'' upon graduation. These languages are generally defined as the less-commonly taught ones, such as Japanese, Russian, Chinese, and Portuguese. Also, the Defense Department has established a committee to study the whole issue of foreign language.
''There needs to be a sign and signal from the federal government that language is a national priority,'' says James Perkins, chairman of the International Council for Educational Development. ''But after that, the initiative has to be carried on from the graduate level on down through elementary schools and into the home. The federal government affects only 5 percent of the overall budget.''