One of the most comprehensive and latest intelligence testing done on boys and girls.

Here are some of the largest studies done on Intelligence of boys and girls. The statement "Boys and girls have on average equal intelligence" does not tell the whole picture.

  1. Population sex differences in IQ at age 11: the Scottish mental survey 1932
    1. Done using 87,498 participants, about 95% of all the 11 years old in whole of Scotland.
    2. Greater Male Variability: Boys and girls had equal means despite the large sample (rather population), however, boys had greater Standard Deviations. Around 1.4 times more males in both the lowest IQs 50-60 (mentally deficient) and highest IQs 130-140 categories (Genius).
  2. Sex, intelligence and educational achievement in a national cohort of over 175,000 11-year-old schoolchildren in England
    1. 175,000 11 year old school-children in England tested, around 93% of the entire population of 11 year olds in 2004.
    2. EDIT: (My bad. These are not 93% of the entire population, but rather 30% of those who took KS2 in 2004 in England. It covered 93% of the educational authorities.)
    3. No sex differences found for average in General Intelligence. Girls had a 0.26d advantage in Verbal, boys had a 0.28d advantage in Quantiative ability, and there was no difference on non-vebal IQ.
    4. Boys also had greater variability, with variance ratios of 1.12 for Verbal, 1.22 for Quantative, 1.14 for Non-Verbal, and 1.16 for general intelligence.
  3. A longitudinal study of sex differences in intelligence at ages 7, 11 and 16 years
    1. Based on the British National Child Development Study that started with all babies born during the week of March 03-09 1958.
    2. Looking at the same boys (N=4626) and girls (N=4458) being tested at each age, at ages 7 and 11 girls had a higher IQ by about 0.9-1 point, however, at age 16 boys scored higher by 1.8 points.
      1. At age 7, girls did better in "Soutgate group reading" (24.29 vs 22.44), boys did better in Problem arithmetic (5.22 vs 5.00).
      2. At age 11, girls did much better in Verbal General ability (23.13 vs 21.05) and Nonverbal General Ability (21.01 vs 20.76), slightly better at Reading Comprehension (16.03 vs 15.93), and boys did better in mathematical (16.81 vs 16.44)
      3. At age 16, boys did better in Mathematics Comprehension (13.39 vs 12.09) and slightly better at Reading Comprehension (25.35 vs 25.27)
    3. Note: I do not endorse the authors of this study, since they seem to be scientific racists, however, the study and its methodologies look genuine and the findings robust.
  4. 4-year longitudinal assessment of language and mathematical performance of all French first and second graders (2,653,082 children).
    1. The study is quite biased and seems to have an ad-hoc explaination that girls' advantage in language is inherent whereas boys' in math was "acquired" through "bias against girls". Here is a great X thread debunking this study and pointing out its flaws (It's in French but Google Translate does a decent job).
    2. Three Math and Language tests done at start of first grade (T1), after 4 months (T2), and start of second grade (T2).
    3. Boys and girls apparently had the same mean on the first Math test (T1) with the well known Greater Male Variability. However, T1 appears to measure number recognitions and counting drawings. Where T2 and T3 actually involves Math operations with symbols. Which shows how disingenuous this whole study was.
    4. The Math gender gap reached a little over d = 0.20 (equivalent of 3 IQ points) by T3. On ther other, hand girls did better on the language portion by d=-0.1935 (2.9 points) in T1, d=-0.0845 (1.2675 points) in T2, and d=-0.1371 (2.06 points) in T3. The differences were present regardless of the other explanatory variables analyzed and uniformly there along all regions, showing this was very likely biologically driven.

So here's something which is quite obvious by around age 11: Boy's and girls have about same overall intelligence, however, boys have greater standard deviations (diversity). Due to this there will be more boys who are geniuses as well more who are mentally deficient compared to girls, though this at the extremes and not noticeable for most.

Girls do a bit better verbally and boys do a bit better in Math/Spatial abilities, boys have a greater standard deviation (diversity) in both.

Therefore, boys will disproportionately make up those who excel at Math but also those who do struggle with Reading and Writing at the lowest, thi could be a result of dyslexia, which affects boys disproprotionately.

This can affect schooling for boys, especially their grades considering their writing and reading skills are on average lagging behind girls, even if their intelligence is the same and might lead to grading bias. Due to this, you'll see boys do decently on standardized tests except for Reading/Writing even if their grades aren't that good.

Poor male verbal ability would probably also mean men would be an overall minority in college, especially in liberal arts, though they will be a majority in Math/Spatial heavy fields Physics, CS, and Engineering provided everything is fair.

There should also be a need for special attention to these poor verbal performers as well, and we can probably encourage them for skilled trades and vocational training.