While the siege dragged on, the governor of St Petersburg, Vladimir Yakovlev, issued a warning against religious sects which, he said, were turning out "zombified children".
However, although police said they had orders not to yield, one officer assured reporters: "No matter what the order is, we will never attack the children."
The siege began on Monday morning when police blocked access to the school, which is run by the Dutch Society for Open Christianity. Only a few teachers and pupils were inside the building at the time. But more slipped in to support the occupation, so that eventually 40 children and 20 adults were inside.
Police said they were enforcing a recent ruling of the St Petersburg City Arbitration Court that the society could no longer use the school rent-free and should leave. The society argued that since it had renovated the building, the rent-free agreement should stand or alternative accommodation be provided.
City officials blamed "irresponsible school staff" for "using children to pursue their goals". Governor Yakovlev ordered his officials to "look carefully into all the religious schools and into what they teach because we already have zombified children".
Freedom of religion is supposed to be guaranteed in post-Communist Russia. However, nationalism is rising and the view is becoming prevalent that a "true Russian can only belong to the Orthodox Church".