A jury at Chelmsford Crown Court took five hours to convict Paul Wilson, 67, who was accused of touching the girl’s breasts and knickers during a massage he gave to her over her clothes.
Wilson, who lives in Nazeing, was cleared of a second charge of sexual assault by fondling the girl’s knee during a car journey and a third charge of sexual activity which involved tapping her bottom with a slipper as a punishment when she made mistakes.
He had denied all three offences which were alleged to have happened between April 2011 and October 2012 when the girl was aged 14-16.
Wilson, who retired from his post as head of maths department at Stewards School in Harlow in 2004, denied that he had touched the girl as she had claimed.
He said she had exaggerated and lied and said it was “a complete mystery” why she had fabricated the allegations.
He expalined that he used the slipper occasionally as a “motivational tool” after the girl’s mother had given her consent.
He also said the stress-relieving massage was agreed beforehand. He admitted he might have “brushed against the very top of her bra” and that his little finger might have gone inside her the waaistband of her jeans.
However, he denied he had any sexual interest in the girl or that his actions were sexually motivated.
Wilson spent 20 years teaching at Stewards School. He also taught at the former Netteswell Grammar in Harlow, Epping Forest High in Debden and at St Julian’s school, St Albans.
Sentencing was adjourned until next month and Wilson was remanded on bail.