In the following passage from The Perks of Being a Wallflower by Stephen Cbhosky, “english” isn’t capitalized:
There is this one girl in my advanced english class named Susan. In middle school, Susan was very funny to be around. She liked movies, and her brother Frank made her tapes of this great music that she shared with us.
As far as I know, English is written with a capital E except for the billiards move. In this book, however, it is consistently written in lower case. That doesn’t quite fit the main character’s personality, but it still could be intentional (the author is trying to mimic teen speech).
Is this a mistake, or is there any reason why advanced english class shouldn’t be written with a capital E?
You are right. English, when referring to language, the people, or the country, would always be conventionally capitalized. The text does use conventional capitalization for the first word of sentences, the pronoun I, for names of other people and places, and so on, so the non-capitalization of English stands out as unusual.
The book is written in an epistolary format, a style which is more conversational than narrative, and which therefore may dispense with strict adherence to conventions of grammar, usage, or orthography. In such a style, one might not capitalize English as the name of a class, advanced english class being parallel to math class or gym class in the American vernacular.
On the other hand, English is lowercase only in its first few appearances. Later, he writes
He really likes teaching kids English and thinks maybe he can take over the drama department, too, next year.
Bill gave me my first B in advanced English class for my paper on Peter Pan!
This makes it hard to know whether the inconsistent capitalization is intentional— perhaps to indicate more careful writing as the author matures, or that adolescents are not attentive to orthographic matters— or whether it is an editorial or typographical error. Both French fries and french fries are used, for comparison, but instances of Chinese, Greek, and Indian are capitalized throughout.