Mexico Teacher Strike Tests Salinas.SCHOOL OF HARD KNOCKS. Action underscores difficulty of tackling entrenched corruption and educational malaise.

CARLOS Salinas de Gortari forgot to shut the lid on Pandora's box. The young Mexican President seemed to have little trouble prying it open in January, when federal agents burst into the fortress of corrupt oil-union boss Joaqu'in Hernandez Galic'ia and put him behind bars. Mr. Salinas followed up quickly by jailing a fraudulent financier in February and nailing the ``godfather'' of Mexican drug trafficking last week.

But now comes the hard part.

For the blows not only distracted attention from Mexico's ever-deepening economic crisis, they also unleashed a wave of union dissidence that, ironically, is now seen as Salinas's severest test. On Monday, an estimated 500,000 members of Mexico's teachers' union - which, at 1.1 million members, is the largest union in Latin America - launched a strike aimed at doubling their salaries and removing a corrupt union leadership they describe as ``a Mafia.''

As several million Mexican children are forced to play hooky, Salinas is under intense pressure to revitalize a neglected educational system and sack the union's notoriously corrupt leader, Carlos Jonguitud Barrios.

``The dissident movement certainly saw the blow to `La Quina' [oil-union chief Mr. Hernandez Galicia] as a signal that they were free to go after Jonguitud,'' says private-sector labor analyst Raul Vazquez. ``Salinas has gotten himself into a very complicated situation.''

Labor experts and political analysts here say that, unlike Salinas's string of earlier triumphs, this conflict cannot be resolved merely with a spectacular arrest of Jonguitud, who has been charged with milking $9 million from union coffers. NOT only would such an arrest be difficult, since as a member of the Senate, Jonguitud enjoys immunity from prosecution.

But even if Salinas decided to lock the leader up, he would be turning the union over to a left-leaning dissident group and endangering a key network of support for his ruling Institutional Revolutionary Party (PRI).

But Salinas is faced with more than a momentary dilemma. The teachers' strike also reveals an educational system that has been undercut by the country's seven-year-old economic crisis, overlooked by the government, and sideswiped in a game of political power.

``We're playing with the future of Mexico,'' says Ilan Bizberg, a union expert at the Colegio de Mexico. ``Neither the government nor the union has really shown that it's interested in educating our country's children. What has interested them more is political control.''

Even as teachers' salaries have plummeted by more than 50 percent in real terms over the past seven years, the corrupt union leadership itself has flourished. It has increased its political clout, expanded its business empire, and tightened its control over educational posts and policy.

According to dissident members, primary-school teachers who earn an average of $150 a month must pay up to $600 to be assigned their jobs.

The union skims more than $12 million a year from members, who must pay 1 percent of their salaries in dues. And it owns over three dozen department stores, hotels, hospitals, funeral homes, and other business ventures. Total estimated value: $100 million.

The union also rules the system with an iron fist.

Since 1980, more than 150 dissident teachers have been murdered, according to human-rights organizations. The killings have occurred mainly in the southern states of Oaxaca and Chiapas, where this week's strike has had a special intensity.

It may seem odd that the teachers' union has grown at a time when most other unions have been whittled away by the government's program of economic restructuring. But unlike other industries, the educational system is not threatened by imminent closings or layoffs: The schools can't be closed, especially with half the population under 15 years old.

But the union is not the only culprit: Critics charge that education has been sacrificed for the ruling party's desperate need for votes and for the government's program of economic restructuring.

``The teachers have been extremely important electorally for the PRI,'' explains labor expert Bizberg. ``Even last year, they turned out for Salinas.''

(El Norte, the leading newspaper in the northern city of Monterrey, reported in an investigative series that the teachers' union had been used as the primary instrument of fraud in Salinas's slim election victory last summer.)

By helping the PRI consolidate votes, labor peace, and campaign donations, Jonguitud has been amply rewarded. The union now controls 16 seats in the lower House of Congress, 42 seats in state legislatures, and more than 100 mayoralties.

Jonguitud himself, while no longer the nominal leader of the teachers' union, is now a PRI senator after serving for several years as governor of San Lu'is Potosi State. BUT the government has also given education a low priority.

According to economist Eduardo Guzman, the budget resources allocated for education dropped from 2.7 percent of Mexico's gross national product in 1972 to only 1.9 percent in 1986 - even as the entire budget itself shrank dramatically. (The United Nations recommends that at least 6 percent of a national budget be allocated for education.)

The government argues that with debt-service payments soaking up to 70 percent of public spending, the budget for all social services - including public education - has to be shrunk drastically.

But Salinas is now finding that some Mexicans have reached the limits of their patience. Unless he can ease the economic burden, the political situation may soon turn uglier.

``By the end of the year, Salinas is going to be judged not by how many people he put in jail but by how many dollars he has put in people's pockets,'' says political scientist Adolfo Aguilar Zinser.

``Salinas's honeymoon is fragile because it's based on the impact that all these jailings have had,'' Mr. Zinser says. ``But there is no substantial breakthrough in terms of the conditions that people endure in Mexico.''