A Parent has complained her five-year-old daughter was taught sex education at a school in Hobart and revealed she was assaulted by two boys in her class just after the visit from Family Planning.
The claims have prompted calls for the course only to be taught with parental consent.
The parent, who did not want to be named, said her kindergarten child had come home and "said the word vagina".
"I was shocked," she said.
"They were taught what a penis and a vagina was, which I don't think they should in kinder.
"I told the principal if I had known anything like that was going to happen, I would have kept my kids at home all week."
The parent said her child told her about the alleged assault when she put her to bed that night.
"That's when she told me that two boys in her class had put their hands down her pants, and she said she bashed them," the mother said.
"She said it happened in the dolly corner.
"There were three adults in the room and 16 kids and no one saw it. She said she did tell the teacher, but the teacher seems to think she did not tell."
Pembroke Labor MLC Allison Ritchie said the allegation would be investigated.
"I have had an undertaking from the Education Minister's office that this incident will be fully investigated," she said.
"The boys putting their hands down her pants."
Ms Ritchie said she had also heard complaints from people delivering the course, who had turned up to a school in the North-West only to find parental consent had not been sought.
She said the children were part of a protective behaviours course.
The complaint parent said her six-year-old and nine-year-old children had all been put through the course.
"I never knew it was happening until they all came home and said," she said.
"I don't think they should do it at that age, maybe Grade 6 or Grade 7, not kinder and prep.
"But the principal said the Government said it was compulsory for kids to learn about their bodies at that age.
"They told me that it was Family Planning, they came in to talk to the kids about their bodies, who could touch them and who could not."
Ms Ritchie said all schools should ensure that parents had the opportunity to give their consent and view the content of such courses.
"Parents should absolutely be able to opt out," she said. "It is not compulsory for every child.
"You might say I am happy for my Grade 7 child to participate, but not my kinder child."
Ms Ritchie said most schools were doing the right thing and gaining consent.