A driving instructor who encouraged girls to kick him in groin has been jailed for four years.
David Aston, who met one of the girls over the internet, was convicted by a jury of two counts of sexual activity with a child and four of causing or enticing a child to engage in sexual activity.
The 32-year-old twice stripped naked from the waist down, crouched on all fours on a towel in woodland near Bicester and encouraged four girls to kick him in the groin until he could no longer handle the pain.
Today Judge Julian Hall sentenced Aston, of Bell Close, Cassington, to four years and ordered him to be on the sex offenders' register for life.
He is also banned from working with under 18s or from communicating electronically with them if it is sexual in nature.
Judge Hall told Aston at Oxford Crown Court: "You indulged in what was old fashioned lewd behaviour.
"People can conduct their own sexual behaviour in private with consenting adults to their heart's content.
"But if you do it with children, with people under the age of 16, it is absolutely disgraceful.
"You skew people's lives in that way."