When Minister of Education Carios Tunnermann Berheim arrived this morning at the Primary School of the Heroes and Martyrs in the Rene Shick neighborhood, he was greeted with warm applause by the 1,200 children, 24 teachers and 50 or so parents who had gathered outside on the school's grassy playground.

Tunnermann's arrival -- in a white Mercedes Benz that once belonged to former president Anastasio Somoza -- was unexpected. Olga Pineda Delgado, a sixth-grade teacher, said exictedly that a minister of education never before had visited the relatively modern, although poorly equipped, school, located in one of Managua's poorest barrios.

The excitement grew as the students first sang the stirring, melodic "Hymn of the Sandinista Front," and then heard Tunnermann tell them that they "will have a privileged place in the new Nicaragua because you, the children, are the hope of the country and the revolution."

Today marked the unofficial reopening of Nicaragua's public school system, which has been closed since May, when the fighting here was so bad and the streets throughout the country so unsafe that it was decided that the system's 500,000 primary and secondary students would be better off at home.

For the next month, the schools will be open and their teachers will be in place but the normal cirriculum will remain suspended. Instead of learning how to read, write and do arithmetic, the children will spend their time learning about the Sandinista revolution, its history, principles and goals.

"Many of these children have seen their fathers or their brothers killed. Some of them have had their homes bombed and all of them have suffered," Tunnermann explained during the short ride between his office and the recently renamed Heroes and Martyrs School, which used to known simply as the First Step Elementary School.

"We decided that we had to explain to the children what had happened before the regular school year begins again" on Sept. 16, the minister said.

Each school in the country will use the coming month to acquaint its students with Nicaraguan history -- to be taught by the system's 10,000 teachers, who spent the last two weeks attending special courses designed to teach them how to present the material.

In addition to the history lessons and discussions, Tunnermann has asked the schools to organize recreational activities, and requested teachers to treat students with flexibility and understanding, to give them an opportunity "to recuperate the joy of living" after the months of fighting most have witnessed.

At the Heroes and Martyrs School today, a small group provided music for the children and eight high school students presented a folklore show of native Nicaraguan marimba dances.

But at the heart of the month's activities will be the courses about the revolution. Their content will undoubtedly be of great interest to local and foreign observers, who will be watching to see whether it explains or indoctrinates -- as a probably indication of what kind of school system the new government plans to create.

The country clearly needs a better system of education. According to statistics compiled by the Samoza government, based on a 1971 census, 42.1 percent of the country's 2.5 million people are illiterate and another 20 percent probably are functionally illiterate.

Only 65.3 percent of the children under 12 who should be in school actually attend classes and only about 25 percent of those who enter the first grade continue through high school, according to the official figures.

Of the country's 10,000 teachers, Tunnermann said, many do not have university degrees or regular teaching certificates, especially in rural areas. Teachers at the Heroes and Martyrs School said they earn between $75 and $150 a month.

One of the first things the new government here said it will do is make primary and secondary school both obligatory and free. Tunnermann said it will take some time to implement this policy, however, in part because only 37.2 percent of the country's schools -- limited by a lack of qualified teachers and space -- currently hold classes beyond the third grade.