Three books from the series,written by Enid Blyton. (Books 7 and later were written by Pamela Cox.)

Book 4 - Upper Fourth
The girls are in a higher form now. This year there is the tension of exams for the first time, but there is all the fun of the summer term as well -- and the high spirits of a lively and imaginative form of girls.

Book 5 - In the Fifth
Games, lessons, quarrels and tricks all form part of a lively term, but the biggest event of all is the Fifth Form pantomime, written, acted and produced entirely by the girls. It generates a lot of fun, but also a surprising amount of trouble.

Book 6 - Last Term
In Blyton's final book about the girls at Malory Towers, Darrell becomes head girl. Unfortunately not all the girls are as responsible as she is and in her last term Darrell sees many changes in her old school friends.