OP I'm not sure there is any gender in balance in science at primary, it's just taught really badly, especially now the written SAT has gone and it has been stuffed into a tiny corner of the time table.
I have DDs either side of the change, DD1 did loads of science (I think the SATs syllabus was awful, but at least they did science).
DD2 seems to have been given a, teacher assessor, L5 having done nothing.
That a more general English is for girls, especially with fucking Gove worrying about hand writing and grammar, and maths is for boys bias exists at primary I have no doubt.
It happened DD2 was best at English and one of the boys best at maths.
(Just happens one has a maths teacher mum and the other English teacher grandparents).
Not until they thought they might get some L6s did primary push DD1 or any of the other girls (or table 2 boys) particularly in maths and I don't thing the reverse happened in English either.
Certainly merit certificates were DD2 English, usual boy for maths the whole way through.
In other classes too there was a bias for English girls, maths boys or simply English girls, no certificates for boys.
Or to put it briefly, primary seems to roll with what DCs are naturally good at. Given the greater maturity of girls in reception/Y1 often means their reading, comprehension and writing are often better than the boys and their writing neater. English becomes a girl thing.
That leaves maths where the answer matters and tidiness is much less important for the boys.
(And Dyslexic, worrying haters like DD1 and me!)