In Nicaragua illiteracy is out, ideology in

It is 8 in the evening - a bit late for Nicaraguans who will get up at 5 or 6 in the morning to be at work by 8 o'clock. The air is still, humid, and sultry. It is the sort of day when Managuans try to be out-of-doors.

But here in a working-class sector of this capital city, in a schoolroom with crude brick walls and light from a single brilliant neon tube casting shadows into corners of the room, two dozen men and women are seated on wooden benches at much-battered school desks that have been used for decades.

The small group is part of a popular-education collective - Nicaraguan adults , some in their 20s but most over 40. Many of them are going to school for the first time. Those who cannot read and write take basic literacy courses and eventually move into classes in simple geography, history, and economics.

Those in this classroom, many of whom have learned to read in the five years since the Sandinista guerrillas took power here, are in their 50s and 60s. This evening, they are discussing Nicaragua's economy and trying to make sense of it.

Many are not quite sure where Nicaragua is. So Blanquita, their teacher, who is a university economics student, goes to a map hanging over the blackboard and points out Nicaragua's location as well as its relationship to the rest of Central America and to ''the enemy, the United States.''

Blanquita smiles as she talks of ''Nicaragua's potential.'' She cites figures of cotton and coffee production, adding that ''it would be much more if the United States did not blockade our homeland.''

She holds up a spool of cotton thread she purchased that morning in a market and tells the class that Nicaragua exports crude cotton right off the plant to other countries, which turn the raw material into dress and shirt material and into thread. She explains:

''When a country exports a raw material, like cotton, and then buys a finished cotton product like thread, it loses on the deal. The raw material sells for less than the thread. It costs money for the machinery that makes the thread. That is added to the cost of the cotton, and therefore the thread costs more.

''We should be making thread here,'' she adds. ''Then the thread would not be as expensive. Sometime in the future, we will make it.''

It was a simple lesson in economics - laced with a political message. All over Nicaragua, similar lessons are taking place. For the most part, the students are adult Nicaraguans with limited formal education. The teachers are often teen-agers or university students in their early 20s, like Blanquita.

In a nation beset with staggering economic, political, and social problems, Nicaraguan leaders are proud of the progress they are making in education - for school-age children and adults.

The Sandinistas note that, when they came to power in 1979, 52 percent of the population over 10 years of age was illiterate. They compare that statistic with the 4 percent illiteracy in Costa Rica, their neighbor to the south. They also cite Cuba's illiteracy rate of 23 percent in 1959, when Fidel Castro came to power, saying that ''the situation here was worse.''

Within 15 days of their victory over the dictatorship of Gen. Anastasio Somoza Debayle, the Sandinistas announced their educational goals and a program to carry them out. Drawing on Cuba's approach to wiping out illiteracy, the Sandinistas ambitiously promised to eradicate illiteracy by 1981. They funded the program with $25 million. To actually carry out the task, they imported Cuban teachers and drafted university students out of their classrooms in a massive, nationwide literacy campaign that reached every corner of the nation.

They quickly ran into problems. Many Nicaraguans resented the Cubans, and some Cubans were run out of villages by natives. At least five Cubans were killed. The university students, too, were sometimes resented by local people.

On balance, however, the program was a success. It didn't meet the 1981 goal, but illiteracy now has been largely eradicated, and the second phase of the program - that of providing classes beyond literacy courses - is under way.

Concurrent with the literacy campaign and subsequent effort to bring courses in basic subjects to all Nicaraguans, the program has sought to expand educational opportunity to Nicaraguan youth, providing both grade and high school classes. ''We now can guarantee that every child in Nicaragua will be literate by the time he is 12 and that virtually all children will get a primary (grade) school education and many a secondary (high) school education,'' says a Ministry of Education spokesman.

Heading the program through the five years was Education Minister Carlos Tunnermann Berheim, a leading civilian opponent of the Somoza regime and rector of the National University during the 1970s. He recently left the job to become Nicaraguan ambassador to the US.

Most observers say he and his ministry have done a good job in eliminating illiteracy and in providing education to both young people and adults in Nicaragua. There have been criticisms of the political content of the education, particularly in the adult-education phase. One textbook, the 126-page ''Dawn on the People,'' is offensive to many Nicaraguans. Used primarily in the literacy campaign, it is said to indoctrinate the population with Sandinista philosophy.

But there is no certainty that all Nicaraguans are buying the philosophy. Many were more interested in learning to read and write than in the political message.

Still, there can be no denying the political content of education here. Teachers like Blanquita, moreover, do not deny that the teaching has such content. ''After all,'' she says, ''politics is an essential ingredient of all teaching.''

Friday: Report from Costa Rica