Ministers have stuck by their guidance on LGBT lessons in schools despite concerns it was putting head in the firing line, but have won union support by strengthening their expectations around the issue.

Schools Week reported earlier this year how headteachers were concerned about the draft guidance for teaching relationships, sex and health education.

The guidance, finalised today, still states that it is up to primary school heads to decide whether teaching about LGBT relationships is age-appropriate for their pupils – which heads had said left them in the firing line over parent protests.

But education secretary Damian Hinds said today he would “strongly encourage” primary schools to discuss with pupils how there are “different, strong and loving families, including families with same-sex parents”.

The stronger language seems to have got some detractors onside.

Paul Whiteman, general secretary of the National Association of Head Teachers (NAHT), which had previously raised concerns, said Hinds had “strongly encouraged every primary school to continue what they are already doing – to teach about relationships in an inclusive way”.

“Today’s statement is a clear signal to schools, that when it comes to talking to pupils about the different kinds of families and relationships they may encounter in their lives, it’s a question of ‘when’ and not ‘if’.”

However Schools Week understands the union will continue to push for the guidance to also be beefed up.

The NAHT passed a motion at its annual conference in May calling for a “more robust and legally-enforceable policy and support for schools as they carry out their public sector equality duty”.

One head warned protests against LGBT relationships education at schools across England are being exacerbated by unclear government guidance.

Whiteman added today: “We will continue to work alongside the schools where we have seen protests and objections, to help everyone involved restore a peaceful and productive teaching and learning environment.”

From September early-adopter schools will begin teaching the new content, before a nationwide roll-out in 2020. The government will also publish details of a new working group shortly.

The finalised guidance published today is mostly the same as the draft guidance published earlier this year.