A Fortunate Term: A Romance Classic By Angela Brazil

Angela Brazil (30 November 1868 – 13 March 1947) was one of the first British writers of "modern schoolgirls' stories", written from the characters' point of view and intended primarily as entertainment rather than moral instruction. In the first half of the twentieth century she published nearly 50 books of girls' fiction, the vast majority being boarding school stories. She also published numerous short stories in magazines.

Her books were commercially successful, were widely read by teen girls, and influential upon their readers. While interest in girls school stories waned after World War II, her books remained popular.
Excerpt:
“Mavis, at the time our story begins, was fifteen and a half, and exactly fourteen months older than Merle. It is necessary to state her age, because people always forgot it, and set her down as the younger of the two. Everybody, friends and strangers alike, gave precedence to Merle, the taller, stronger, more confident, and more dominating individuality. Mavis was an ethereal little person, who might be described as a spirit very lightly embodied in flesh. With Merle soul and body were balanced, with a bias towards the latter--on the whole she was of the earth, earthy. There was a sufficient likeness between the sisters to suggest that nature had reproduced an identical type in different mediums. She had painted the first delicately in watercolors, then had copied the same model more strongly in oils. Which picture you preferred was a matter of taste.
Fortunately there was a complete understanding between the girls. Their particular faults and virtues seemed to dovetail into one another without friction, and they were excellent chums, a useful factor at school, where Mavis often needed a defender, and Merle was constantly requiring the services of someone to help to pull her out of her numerous scrapes”....