Mark Robertson repeatedly carried out a sex act on the girl in a house near his home. The physics teacher also admitted participating in sexual conversations on the internet.
At Aberdeen Sheriff Court yesterday, Robertson, 37, pleaded guilty to engaging in sexual activity with the girl on various dates between 14 December, 2007, and 11 January, 2008.
He had been suspended from his post at Portlethen Academy in Aberdeenshire while an investigation was carried out last year.
Yesterday, defence lawyer David Moggach said Robertson was now receiving counselling.
The original charge against the teacher, from Cove Bay, stated that he had carried out lewd acts against the girl for three years and had also performed a sex act over an internet webcam.
However, the Crown accepted his not-guilty plea to that part of the charge and it was dropped.
Sentence was deferred until next year for background reports.