The argument about the relative importance of sex and gender identity – whether someone feeling they are male or female should replace the reality of sex in law and society – has become one of the most polarising identity issues of our time. But out of this toxic mess a sensible consensus has emerged: both parties have largely ditched commitments to enshrine in law the view that people should be able to self-declare their sex for legal purposes. It has at last been acknowledged that this would effectively dismantle women’s hard-won legal protections for single-sex spaces, services and sports, and these are not inconsistent with robust anti-discrimination protections for trans people. But profound disagreements within government and across the public sector continue to leave a policy vacuum that is being filled by activists with no understanding of existing law on sex and gender. Nowhere is that more true than in schools. Ministers have for years been delaying guidance to help schools respond appropriately to children experiencing gender distress; guidance that headteachers are desperate for in a world where adult activism has corrupted any hope of a shared understanding of the clinical evidence and existing law as applied to children. On what constitutes clinical best practice, the “affirmative approach” is an ideological position grounded in a belief everyone has a gendered soul separate from their sex. So when children experience gender distress, it is a sign their gender identity differs from their sex and they should be affirmed as the opposite sex (to explore other reasons for their distress is to deny their identity); appropriate ways of treating gender distress include puberty-blocking drugs, then cross-sex hormones. The evidence-based position is embodied by an independent review for the NHS by the distinguished paediatrician Hilary Cass. Its interim report underlined the lack of evidence for the affirmative approach that parts of the NHS have been pushing on children. Gender dysphoria is a clinical condition in children; gender distress can come and go until the early 20s and in most young people resolves itself, so may be but is usually not a sign a child would go on to develop an adult trans identity. It can be associated with autism, children grappling with same-sex attraction, childhood trauma including sex abuse, and discomfort about puberty. Children have been prescribed puberty-blocking drugs despite the fact they may inhibit gender distress resolving itself and cause long-term consequences for fertility, bone health and brain development. Critically for schools, the Cass review says that “social transition” – treating girls as though they were boys and vice versa – is not a neutral act, but an active intervention that can have long-term effects on psychological functioning. NHS guidance now says it should only be done to alleviate clinically significant distress or impairment in social functioning. Before the Cass review, I had assumed social transition was pretty harmless. The reality is that it probably beds in, psychologically and socially, what might otherwise be temporary gender distress; and in young children who don’t have the capacity to understand they haven’t literally changed sex, it is effectively misleading them about reality. It should not be done without input from mental health professionals; it certainly is not something schools should be leading on. A “watchful waiting” approach that allows children to experiment while experiencing neither celebration nor negative reaction from adults will be more appropriate for most. Moreover, the law means schools are tightly proscribed in terms of what aspects of social transition they cannot facilitate. Safeguarding law requires schools act to protect children from harm and promote their welfare. They must not discriminate against children experiencing gender distress, but this does not oblige schools to treat them as though they were of the opposite sex. In fact, there are specific areas where it is unlawful to do so, for example when it would undermine the safeguarding of that child or other children. Schools are obliged to provide single-sex toilets for over-eights and changing facilities for over-11s. To force other children to pretend another child is of the opposite sex, for example through mandated pronoun policies, is likely to constitute belief discrimination. They cannot do anything that would constitute sex discrimination against other children; for example, in relation to competitive sports or sleeping arrangements on residential trips. And schools must be politically impartial: they cannot teach partisan ideology such as the idea that everyone has a “gender identity” and sex is “assigned at birth” as fact, only as a contested set of beliefs. Campaigning groups with ideological positions so blunt they cannot possibly accommodate these complex medical and legal positions have stepped into the gap left by government. Trans inclusion toolkits have been produced for schools that are uninformed by evidence on child development and safeguarding and include legal misinformation such as telling schools they must treat gender-questioning children as the opposite sex for all purposes. Many schools rely on relationship and sex education materials produced by external groups that teach gender ideology as fact, in a way that reinforces rather than challenges damaging sex stereotypes and may well encourage gender distress in vulnerable children. The school system is decentralised, so it is hard to know the scale of the problem; many schools will be getting the law right. But there are troubling stories of schools facilitating children’s social transition without parental knowledge because they wrongly categorise a parent who shares the Cass review’s concerns about the affirmative approach as a safeguarding risk to their own child, or wrongly believe a child must consent to information being shared with parents. And of children being referred by schools to affirmative charities that help them access harmful breast binders, or even GPs who prescribe puberty blockers or cross-sex hormones without parental knowledge, let alone consent. One parent I spoke to discovered that, even where a head agreed with her and her child’s psychologist that watchful waiting was the right approach, other senior staff disregarded the head’s directions. These cases are examples of the state actively undermining children’s relationships with their parents, purely because some teachers believe they know better than parents and clinical experts what is right for a child. Children experiencing gender distress need access to holistic mental health services that address all possible causes of that distress; schools need to support them to access education without undermining their wellbeing through inappropriate interventions or discriminating against other children. The first step in helping schools understand their role has to be comprehensive government guidance on how to do this in a way that is commensurate with the law, the medical evidence and their duty of care to all children. Sonia Sodha is an Observer columnist