Paris — What do former Gaullist Premier Jacques Chirac and leftist leader Jean-Pierre Chevenement, a former industry minister under the Socialists, have in common? Both are graduates of the prestigious Ecole Nationale d'Administration (ENA). The graduates of this Paris-based school, which provides training for the higher ranks of the civil service, form a strong ''old boy'' network in French public life. Not only do they dominate the ranks of the country's political leaders, but they also fill the top levels of the ministries, especially in diplomacy and finance.
In addition to Paris Mayor Chirac, four ministers of the present Cabinet and opposition leader Valery Giscard d'Estaing also attended the school.
But ENA, so sure of its preeminent role in French society since its establishment in 1945, is now under attack.
Despite the preponderance of the school's graduates (they are called ''enarques'') in his government, Socialist President Francois Mitterrand feels ENA has become too powerful and elitest. To the fury of conservative politicians and many of the school's students, he has introduced a plan to democratize the institution.
Starting next fall, ten students out of a class of only 150 will be able to gain acceptance without taking either of the two tough entrance examinations. Instead, they will have worked 10 years in either trade unions or local government and will have passed a separate, less difficult exam.
''ENA must be opened up,'' explained Pierre Laborey, the civil service ministry official responsible for implementing the reform. ''Students now come from privileged backgrounds, and most have attended the same school (Institut d'Etudes Politiques de Paris) before entering. Students from more modest backgrounds who don't have this book-learning but who have a knowlege of real life should be let in.''
Opponents of the reform admit that nearly 80 percent of ENA's students come from upper-class or upper-middle-class homes, and only 4 percent from working-class backgrounds. But, they say, the government is using ''democratization'' to threaten the independence of the civil service by turning the school into a left-wing breeding ground.
The fear stems from the fact that the candidates for the back-door exam will have to be approved by the Communist secretary of state, Anicet le Pors. Le Pors , the critics complain, will favor candidates from the unions, especially the country's most powerful union, the Communist-led CGT.
''The remedy is worse than the problem,'' argued neo-Gaullist assemblyman Jean Foyer. ''The government wants to engineer the exam in favor of its political friends. Placing people at the high level of the administration because they hold 'correct' political views is the essence of totalitarianism.''
Laborey bridles at such criticisms, insisting that the candidates will also have to be approved by a jury selected by ENA's director, Simon Nora. Though selected by President Mitterrand, Nora is not a member of the Socialist Party and has the reputation of being a man of strong independence. With this safeguard, ''there is no risk of politicization,'' Laborey says.
ENA students themselves do not fear communist infiltration. They say they make up a meritocracy that already cuts across political lines. As proof they point to the variety of political views held by past enarques who range, of course, from Chirac to Chevenement.
''The school is divided 50-50 along political lines, just like the nation,'' said an ENA student. ''Probably a majority voted for Mitterrand and there are already Communists enrolled.''
Nevertheless a recent poll shows that 70 percent of the students oppose the reform. They fear that the new two-tier system will lower the quality of the French civil service. The ''back door'' students will not take any of the tough business-school style courses in economics and law. Instead, they will follow a separate, less demanding curriculum.
''That's the fundamental problem with the reform,'' said another ENA student. ''We agree that the school is too elitest, but the answer is not letting in tokens for their political views and having them take different courses. This will only produce incompetence.''
ENA teaches competences in a very French, technocratic way. Enarques learn how to solve problems, any problem.
''You learn that there is a right answer,'' said one student. ''And you learn to show that you know the answer - even if you do not.'' Enarques will continue to learn the correct answers, and then be assured of the best administrative jobs.
''The reform is not going to change the ecole itself,'' said its secretary-general, Louis Chelle. ''Students will continue to receive the tools they need.''
The tools, that is, to rule France.