I agree with others that identification is more likely if there is a poor fit with the current school environment - and that girls, stereotypically, are socialised to fit in with their peers better.
There's probably also an innate selection bias based on gender stereotypes. Here's a (likely boring) anecdote. I have 2 DDs who are school age, both very high achieving. The eldest is very good at literacy based tasks and has won a scholarship place to a much sought after school; the school is renowned for its very strong academic results in the later years but possibly is less rigorous at junior level than her current school. She's very good at music and swims competitively and this school caters well for this.
The younger has also been promised a place soon. She is also very highly achieving but the one we had tested as she gets irritable when under stimulated and is mathy. She's been allowed to move at her own pace this year and has finished 3 years ahead in maths, it's a co-ed school but she's easily the school's best maths student. She's at the top of her year for English as well. However, her lovely teacher warned me that each year I'd need to advocate for her to be appropriately extended and that, with her personality, DD would fail to thrive if not extended.
There is a gifted school in the area that we've overall rejected due to its limited sport and extra-curricular activities. In addition, it doesn't do any better overall in its senior level academic results. It does, however, let students work at their own pace at junior school level, and I've been worried that this is what my second DD needs.
I thought it wouldn't hurt to know my options so called the gifted school recently. The (male - I think it's relevant) staff member in charge of admissions confirmed that she'd meet their criteria and asked about her strengths; I said she was very mathy, very good on computers and, according to her teacher, top of the year in science as well. He sort of chuckled and said, "Well, she's the sort of girl who really would have been better being a boy".
I was stunned. And we certainly WON'T be sending her there. And it makes me wonder how many girls are subtly discouraged from displaying maths based skills because they're girls.
