The 51-year-old man was fired last month from the Nänikon-Greifensee school after it was discovered he was convicted for possession of child pornography in 2011 by a Zurich district court, according to a news programme on the German-language SRF network.
The court sentenced the man to a suspended prison term of 15 months and fined him 1,000 francs, Schweiz Aktuell reported.
The man was also earlier convicted for sexually abusing children in Thailand, where he was freed after payment of a surety, the news report said.
Schweiz Aktuell said school authorities only learned of the man’s past through a Google search.
Hansruedi Ammann, chairman of the school commission for Nänikon-Greifensee, confirmed the facts in the broadcast when contacted by the SDA news agency.
Ammann said it was on May 27th that he became aware from another teacher of the man’s past.
The same day the Zurich cantonal education office fired the teacher with immediate effect.
Ammann informed parents in a letter obtained by SDA that an administrative investigation has been launched into the matter.
The news agency said that the man was interviewed before the decision was made to sack him.
The confirmed the past convictions but maintained that the accusations against him were unjustified and that he never abused children, SDA said.
The school commission said the accusations were too serious to allow the man to continue teaching.