Vienna — Slowly improving prospects for easing tensions between Poland's Communist authorities and the Roman Catholic Church have run into fresh trouble - over an old issue.
It concerns the display in state schools of religious emblems, in particular, the crucifix.
Last week it sparked a local confrontation when students protested the removal of crucifixes in classrooms of an agricultural school near Warsaw.
On Saturday, some 700 students continued their protest at the Jasna Gora monastery in southern Poland. Most of the protesters were from the agricultural school at Garwolin, where this new conflict started, but some 20 student groups from various parts of Poland joined in.
Both the government and the church seem concerned that this question should arise at a time when each side was showing some confidence in a turn toward a more stable relationship - including hints of a return to diplomatic relations in the course of this year.
In the current dispute, the authorities have taken their stand on a 1961 law and the constitutional principle of separation of church and state and the lay character of education. The local clergy claim the schools belong to the nation, that Poland is a Catholic nation, and therefore the feeling of a Catholic majority should be respected. (Some 90 percent of Poles are Catholics).
The church has yet to state its position officially. In his only comment so far, the primate, Jozef Cardinal Glemp, said: ''We have had problems with crucifix in schools ever since the last war ended.''
The caution reflects a major difficulty facing the church. Since the Pope's visit last June, it has been trying to broaden the beachhead for dialogue in pursuit of longer-term church aims, including its recognition as a corporate body with a place in the established system. The church's legal status was withdrawn immediately after the communist takeover in 1945.
Since the papal visit, Cardinal Glemp has insisted that ''patient negotiation'' is the only way to improve relations for Poland's social good as well as for the church. That has not gone down well with some younger priests who still defend Solidarity from the pulpit.
They are not so many. But the more outspoken have evoked considerable public support. The transfer of one such priest from a suburban Warsaw church to a country parish prompted strong protests from his congregation, as have efforts to silence others under threat from the authorities for provocative sermons.
Glemp is unlikely to echo the Garwolin protesters' words about ''a war on the cross.'' But he will be under strong pressure from some bishops as well as from radical rank and file clerics to do more than urge priests to refrain from politics for the sake of possible church gains in other fields.
On the government side, Gen. Wojciech Jaruzelski's utterances on the subject of the church suggest that like his predecessor, Wladislaw Gomulka in 1956, he does not underrate its influence among his countrymen. (Gomulka worked out the 1956 concordat that balanced Church support for the regime's election program with official tolerance of Catholic instruction in most schools).
But whether cardinal and prime minister can find a formula to prevent a small-town dispute mushrooming into a national one is another question.