Michael Aldersley, a science teacher at Calderstones school in Liverpool, was sacked in May 2001. In November 2000 he had told a computer class of 14-year-olds: "Everyone in the nig-nog corner, come here, you might learn something." Three pupils and their parents complained to the school.

Yesterday, a General Teaching Council hearing in Birmingham concluded he had demonstrated unacceptable conduct, and that a formal reprimand should lie on his registration for two years.

Dr Aldersley, in his 50s, did not attend the hearing. In a statement, he said he had meant "foolish and silly children". The hearing was told the Oxford dictionary had several definitions of the phrase: a foolish person; an unskilled recruit; or a coarsely abusive term for black people.

After the hearing, Brian Davies, headteacher of Calderstones, said: "I never considered that it would mean silly or foolish children. I only took it to have one meaning ... and that is a derogatory phrase toward black pupils."

Mr Davies said Dr Aldersley had apologised to the pupils concerned, but from his initial meetings with the teacher, he suspected he did not realise the offence he had caused; 22% of pupils are from minority ethnic groups. He was sacked for gross misconduct by a 5-3 vote of governors.

In his statement, Dr Aldersley referred to his "incautious" use of language but said that, when questioned by the school, he had felt a lack of support, a bullying tone, and cynicism concerning racism in South Africa, where he taught in the 1970s. Yesterday Mr Davies acknowledged that Dr Aldersley "nailed his colours very firmly to the mast" in South Africa as an opponent of apartheid. Calderstones colleagues and pupils had also written in support of Dr Aldersley, who had an unblemished teaching record.