The course my older DSs took was W10A - Intermediate Expository Writing (see description below). They recommend taking it with EG20, but the boys didn't have time for more.

EG20 Grammar and Style of the Sentence

This is a self-paced grammar course designed to help 7th to 12th grade students understand the grammar of the sentence and make stylistic choices informed by their knowledge of grammar. Topics include effective subject and verb choice, active and passive voice, clause coordination and subordination, sentence fragments, comma splices and run-together sentences, and phrasal modifiers (including verbal constructions or finite verbs). The course runs over the web. We strongly recommend that students enrolled in the W10 or W11 series also take EG20 concurrently.

Completion time: 1 quarter.

W10A, W10B, W10C Intermediate Expository Writing

These courses introduce students to essay composition in the context of critical reading. These courses are intended for students aged 11 through 13, and for students who have completed W09ABC. Please note, however, that course content may not be appropriate for students under age 11. If you would like to request an exception, contact the English Supervisor. Topics include: literary analysis; argumentative essay composition; critical reading of a variety of fiction and nonfiction texts, including poems, short stories, narrative essays, a full-length dramatic work, historical nonfiction, and editorials. (Reading material can vary depending on instructor.)

Virtual classroom is mandatory. We strongly recommend that students take EG20 concurrently. All students must pass W10A with a B- or better as the prerequisite to W10B or W10C. W10B and W10C do not have to be taken sequentially.