Simple mean differences summarized in meta-analyses do not always adequately describe sex similarities and differences. We investigated sex similarities and differences in academic achievement test scores during childhood and adolescence multiple ways based on composite and subtest scores from the Kaufman Test of Educational Achievement (Third edition) norming sample. Sex differences in means were investigated across achievement domains and ability levels. Test score variance and percentages of scores at different parts of score distributions were also compared across sex. The largest and most consistent sex differences were female advantages in writing tests: Larger advantages were found in more complex writing tasks. Females also showed consistent advantages in silent reading fluency. Males demonstrated advantages in math problem solving that emerged at the average ability level. Females were more likely to be high achievers in reading fluency and written expression, whereas males were more likely to be low achievers in reading fluency and aspects of writing, and very low achievers in word recognition, word recognition fluency, and reading vocabulary. Males were more likely to be high achievers in math problem solving. Analysis that goes beyond simple mean differences reveals important sex differences regarding academic achievement, and theories should account for overall patterns of academic achievement similarities and differences.