At 15, he was 'bottom of the bottom form' in biology and told his dream of becoming a scientist was completely ridiculous.
Yesterday, British scientist Sir John Gurdon, 'the godfather of cloning' proved his teacher wrong in the most spectacular fashion by winning the Nobel Prize for Medicine.
Sir John, 79, was honoured for the groundbreaking discovery that all body cells have the same genes.
It had been previously thought that once a cell becomes a certain type, such as a skin cell, it lost the instructions needed to turn into a piece of heart, or brain or kidney.
The finding, made when he was a young researcher, paved the way for modern stem cell science - especially the idea that a skin cell can be used to repair damaged, dying and worn-out body parts.
Yesterday, Sir John, who still does research each day at a Cambridge University centre named after him, said he was 'immensely honoured' to share the award with a Japanese scientist and would plough his share of the £750,000 prize money into funding PhD students.
The scientist, whose father was a banker in India and mother was a PT teacher, also revealed that science was far from his forté while at Eton.
Not only did he obtain the lowest marks in biology of all the 250 boys in his year but his school report in 1949 described his grasp of the subject as 'disastrous'. It added: 'I believe he has ideas about becoming a scientist; on his present showing this is quite ridiculous.'
Today, that school report, written by a museum curator drafted in to teach after the war, hangs in a frame in his office.
The young Sir John scored just 2 out of 50 for one piece of work and repeatedly got into trouble for insisting on doing things his own way, rather than listening.
Despite being 'bottom of the bottom form' in biology, he went on to study zoology at Oxford.
Sir John, now married with two children, said: 'When there are problems, like when an experiment doesn't work, which often happens, it is nice to remind yourself that perhaps after all you are not so good at this job and the schoolmaster may have been right.'
His breakthrough came when he was a young researcher. He took the genetic material from a cell lining a frog's gut, put it in an empty egg and watched as a tadpole developed. The 1962 experiment marked the first time an animal had been cloned. It proved for the first time that a highly-specialised adult cell still contained all the genetic information needed to develop all the parts of the body.
It took ten years for other scientists to accept his finding and until 2006 for it to bear fruit.
Sir John, who left Oxford to work in the US, before taking up a post at Cambridge in 1971, shares his prize with Shinya Yamanaka of Kyoto University.
Six years ago, Professor Yamanaka built on Sir John's work by using a cocktail of genes to turn ordinary skin cells back into their embryonic state.
Not only are these stem cells ethically sound but they are a perfect match for the person who donated the skin.
This raises the prospect of people being given hearts or sperm or eggs or retina generated in a lab from a sliver of skin taken from their hand.
In the short-term, tissue from such cells offers a window into brains ravaged by diseases such as Alzheimer's and Parkinson's and allows thousands of chemicals to be rapidly tested to see if they have potential as drugs.
- The Daily Mail