The allegation and subsequent arrest sparked a massive police investigation into the Merseyside school, a unit for children with behavioural problems, where he worked.
Over the coming years, detectives interviewed dozens of ex-pupils, including many in prison, and investigations were launched into 91 current and former members of staff. Court proceedings were taken against 26 people, including Dave Jones, former care home worker and current Wolverhampton Wanderers manager.
After a rigorous investigation, Mr Jones, along with the school head, the head's wife and others were cleared of any wrong-doing. But Mr Lawson was not so lucky. The former police sergeant was sentenced to seven years after being convicted of 17 counts of indecent assault. His colleague Basil Williams-Rigby was jailed for 12 years.
The nightmare only ended last March, when Mr Lawson, now 63, and Mr Williams-Rigby, 58, walked free after their convictions were quashed by the Court of Appeal in London. The court was told some of the people who made allegations against them fabricated evidence to secure compensation.
"When the case against me was being made, the police trawled for people to make accusations against me, dangling compensation carrots of up to pound;150,000 in front of them," said Mr Lawson.
Fifty friends and colleagues came forward to testify on his behalf but such was the scale of the investigation that their testimony was scuppered when the police said 91 people from the school had been accused.
More than six years after that June morning, Mr Lawson says the experience has made him more determined than ever to campaign on behalf of teachers and care home professionals wrongly accused of abuse.
He had plenty of time to think about it. He spent much of 1,011 days locked up in Albany Prison on the Isle of Wight - more than 250 miles from his wife and three children in Liverpool. Holed up with sex offenders, he lived in a tiny cell and was forced to "slop out" every morning.
He refused to take part in sex offender rehabilitation courses and, as punishment, his privileges were reduced, including contact with his family.
"I am not depressed and down any more, I remain positive," he said. "I am enjoying life, enjoying being able to walk out of a door in the morning without waiting for it to be unlocked by someone else."
Mr Lawson helped set up Falsely Accused Carers and Teachers (Fact), one of the organisations being represented at next week's conference. He said: "I still think teaching is a noble profession, but I am more determined than ever that the system that wrongly put me away should be completely transformed."