The market is essay-level developmental writing, often referred to as the "bridge" course (to freshman composition). At the developmental level, the bridge course (and texts for it) apes freshman composition but includes more basic grammar review than the typical comp course.
Fiske 250 Words Every High School Freshman Needs to Know
Starting off with a powerful vocabulary is the best way to prepare for a successful, stress-free time in high school. High school opens a world of new ideas and experiences—along with more challenging and sophisticated concepts. Knowing these 250 words will give students the gift of a head start that will last for years to come.