I am hyperlexic: Extremely good at spelling and grammar, and learned to read fluently by age 4, without being taught. I went to the state spelling bee in the sixth grade, putting me above about 99% of students in that respect. I also write well, if the piece of writing is an essay or report. Fiction and poetry are harder for me than for most people, and I am very slow at writing them; but I can write stories pretty well, if I want to.
Math is my worst subject. Strange that I'm a physics major; I have to struggle harder with calculus than most of my peers. Still, I've really fallen in love with calculus; ever since algebra, when math was more than just following steps to the inevitable answer, I've liked math as much as anything else I study.
Hyperlexia runs in our family... it's rather interesting, because the greater the degree of AS we have, the better our writing and spelling skills seem to be.
My little sister, now 11, was taught by my mother to read at 3 and also has no trouble with spelling and grammar. She is as good at writing as I was at her age; and she can write fiction as well as I can today. She has a few Aspie characteristics--formal speech, moderately strong special interests, and shyness--and is probably on the borderline where AS is concerned. She is socially capable enough to escape the worst parts of it, though; and would probably not be diagnosed AS.
My sister, who is now 20, is a good reader who learned to read fluently at age 5 (in kindergarten). She writes only when she has to, but does it well. She has some Aspie characteristics--she's shy and, like me, asexual--but takes mostly after my mother.
My mother, the least AS of us, is a good speller but learned to read only when she entered school and has no interest in writing; when she does write, her punctuation is usually bad.
I'm the only diagnosed Aspie in our family, but the more Aspie characteristics a family member has, the better they seem to be at languages. Interesting... A more thorough study of the connection between hyperlexia, language skill, and AS really should be made.