Teachers from 28 Berlin schools stopped their work on Wednesday.
The education and science union (GEW) had called for the warning strike, in which around 500 teachers took part according to their own statements.
A bicycle demonstration took place during the warning strike, to which around 400 participants were registered, according to a police spokesman.
Berlin - The union calls for a reduction in classes to be stipulated in a collective agreement.
Teachers would be relieved by less noise, less preparation and follow-up work and less correction effort.
As early as June, according to the GEW, the responsible senators were asked to start collective bargaining on a health protection collective agreement, which the Senator for Finance rejected.
For this reason, the warning strike was the next step to put pressure on the employer, it is said.
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"We hope that we are now ready to talk," said the GEW spokesman, Markus Hanisch.
The corona pandemic was a huge burden for families, which is why the GEW only called a few schools to go on a warning strike.
However, if the blockade persists, the union could call for further warning strikes in even more schools.
dpa