It was a source of relief when, rather than receiving the extensive opt-outs that many feared, the bill introducing compulsory sex and relationships education (SRE) for all children, made it clear that state-funded "faith schools" would have to follow the same principles as all other state-funded schools. By those of us who had feared much worse, these general principles – though not perfect – were considered an acceptable minimum.

Now, with parliament on holiday and late in the day, Ed Balls has tabled an amendment to his own bill, which would exempt state funded faith schools from even the modest requirements that it currently proposes to place on them and the Catholic Education Service of England and Wales have proudly announced that it was their lobbying that won it. We should not be surprised. This is just the latest in a 12-year catalogue of concessions and exemptions made to state-funded faith schools, from a widening of their ability to discriminate on employment, to their continuing discriminatory admissions practices.

Let's leave aside for one moment the question of why a government should be so keen to trade children's rights for Catholic approval in this way, and of why lobbying by an unrepresentative minority should skew the entitlement of pupils in a third of all our state schools. Let's instead take a closer look at precisely what it is that the Catholic Education Service found so objectionable that they had to be exempt from it.

The principles in the bill that schools must follow are that "information presented ... should be accurate and balanced", that the subject should be "taught in a way that is appropriate to the ages of the pupils concerned and to their religious and cultural backgrounds and reflects a range of religious, cultural and other perspectives", that it should "be taught in a way that endeavours to promote equality, encourages acceptance of diversity and emphasises the importance of both rights and responsibilities." These are the principles from which Ed Balls' amendment would exempt faith schools if they say it conflicts with their "religious character". This has rightly provoked outrage, from multi-faith and belief coalitions like Accord and children's rights campaigners.

In a further weird twist, having done this, the government then tried to say it hadn't. They said yesterday that all schools will have to teach SRE "in line with the principles outlined in the bill including promoting equality and encouraging acceptance of diversity" which, if they believe it themselves, means that they don't understand their own amendment, since the effect of their amendment is precisely to allow faith schools not to do this, if they believe it conflicts with their religious character.

The most shameful consequence of the amendment is that it would shift the focus of the law as it applies to faith schools away from the needs of children, towards the religious prejudices of the school, as if this is what the law should really be protecting. Who is education supposed to benefit – the child or the church?