Tayla Lee Brailey was arrested last August at a school in southwest Sydney, accused of having sex with the 17-year-old during class hours near the high school where she taught.
The 32-year-old was also charged with sexually touching a 16-year-old student and inciting to have sex with her.
More than 18 months after she was charged, Brailey pleaded guilty in Campbelltown Local Court on Wednesday to having sex with the 17-year-old student and sexually touching the younger student in separate incidents.
Information tending to identify either child cannot be published for legal reasons, preventing media from naming the school where Brailey worked.
The former teacher also pleaded guilty to using a carriage service to access child abuse material and transmit child abuse material to herself.
Five other charges, including inciting the 16-year-old to have sex with her and aggravated sexual assault of a victim under her authority, were withdrawn by the prosecution.
Brailey will be sentenced in the NSW District Court on a date that will be decided when she returns to court later in March.
She remains on bail under strict conditions which prohibit her from entering any educational institution or being in the company of a child unless a carer is present.
1800 RESPECT (1800 737 732)
National Sexual Abuse and Redress Support Service 1800 211 028
Lifeline 13 11 14
Kids Helpline 1800 55 1800 (for people aged 5 to 25)
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