It had been reported that Sir Leslie was the first serving head to be so honoured - but it turns out that he is the second.
Sir Godfrey Cretney, the head of Regis School, a pioneering comprehensive - only a few miles from Sir Leslie's school in Wolverhampton - was knighted 32 years ago.
Audrey Boliver, the former head of history at Regis School, said: "I was really irate when I heard that people were saying Sir Leslie was the first head to be knighted. With all respect to him, he has only been at Northicote for two years, while Sir Godfrey was at Regis for more than 15."
While Sir Leslie is being championed for the impressive turnaround of a failing Northicote School, Sir Godfrey's efforts to spread comprehensive education during the 1950s appear to have been forgotten. His knighthood came in 1966.
Sir Godfrey's former colleagues remember a man committed to education opportunities for all and who was so proud of his new school that he spent his lunch hours picking up litter in the playground.
Arriving in Wolverhampton from the Isle of Man - where comprehensive education already existed - Sir Godfrey established Regis School in 1955 in the upmarket area of Tettenhall.
It was one of the first four comprehensive schools to be launched in England and considered revolutionary at the time.
When the school opened in September 1955 with 206 pupils, many of the buildings were only half-finished but the idea behind the new establishment was fully developed. "Sir Godfrey was totally committed to comprehensive education and took in pupils of all abilities," said Eva Johnson, secretary to Sir Godfrey from the school's opening until his death in 1971 aged 59.
"Although they were 11-year-olds many couldn't read or write when they arrived but caught up during their time at the school and even went on to university.
"I had heard people saying that Sir Leslie was the first head to be knighted in office and I'm pleased for him, but he was not the first and I felt cross about the mistake.
"Sir Godfrey was an exceptional man. He was strict, but his charm and appeal to children meant he could always get them to do what he wanted.
"He attracted the best teachers from all over the country to come and work at the school and visitors from all over the world came to see an experiment in practice."