An Education Department investigation cleared the group of breaching the ACT Discrimination Act and the guidelines for religious teaching in schools.

The group was cleared of vilifying homosexuals, comparing gay sex to bestiality and warning students as young as 13 that sex was bad and would lead to AIDS and other sexually transmitted diseases.

But the investigation found students had been shown a video that implied teenage pregnancy was a boy's fault, and that bestiality and girls dressing provocatively had been discussed with underage students. Canberra High School was also criticised for not undertaking a ''rigorous process of selection'' before inviting the group to speak to students.

All non-government groups will now need Education Department approval before visiting schools.

Parent David Gould, who originally aired concerns about the group, said he still had concerns.

''The concerns I have are regarding how students' impressions were gathered by the investigation. Seven responses were gathered from students but it isn't made clear how those seven students were chosen and why they are a representative sample. So I've asked for clarification on that point,'' he said.

Mr Gould said he felt vindicated.

Education Minister Andrew Barr said Focus on the Family would need departmental approval before returning to ACT schools.

''They are not banned, but to present in the future they and all other groups will need to go through a strict vetting process and parents will have the ultimate say,'' he said.

The previous opt-out policy would be reversed, meaning parental approval would be required for students to attend presentations by any external organisation.

The Australian Christian Lobby called on Mr Barr to apologise for ''demeaning Focus on the Family''.

Managing director Jim Wallace said Focus on the Family's good reputation had been jeopardised by an ''obvious over-reaction to an isolated complaint''.

Comment was sought from Focus on the Family chief executive Brett McLeod.