Daughter not allowed to do separate Science GCSEs

Yes it will be Double not Triple , so still all 3 subjects. ds is doing Double , probably there is an element of the Science teachers wanting record best grades but also because he isn't going to purse Science A levels so doesn't need the additional pressure and can focus on the coursework so far. I'm confused though , either she has taken GCSEs and got those grades or she hasn't, she wouldn't take them again surely.

It really doesn't matter. Of my very anti-science sons, one DS did triple and got BBB, another did double and got AB with a lot less trouble. Unless she's super-top-flight scientist, double is OK for most things. I was distraught when DS2 was "put down" to double science but five years down the road, it doesn't matter one jot.

What is the school's normal grade requirement for progressing to single sciences?

As she "admits to not trying very hard", then I think you might find an uphill battle to persuade the school.

Unfortunately, your DD is learning the hard way round that there comes a stage when achievement, not just one teacher's view of your potential, is what will matter.

You need to be prepared to support you DD should the school not drop its normal requirements for her (and it is likely they won't - requiring a certain grade and sticking to it are absolutely normal for both state and private sectors). What is it she wants to do after A levels? What is best of the choices remaining to her?

And, of course, supportive messages about self-worth in general and what she can learn from this. If you are lucky, you and she will find the motivating angles from this, and that could make a huge difference to whether she learns to apply herself consistently.

But it won't be separate science and combined science will it? Surely double or triple - so one-third chem, biol, physics whichever option?

I'd go with the school on this unless you really feel she is very good at science and definitely wants to do science A levels. The school may feel two high grades are better than three mediocre ones, and they may well be right. The main thing is that she realises that these exams are all important and works hard this year.

The school is more worried about its results than your child. She is clearly capable of passing all triple science but possibly not getting straight As. I would speak to them again but bear in mind that their say is final

Stick to your guns. Meet the head - consider changing schools. Good luck.