Levels A through F in the BJU Press Vocabulary series are for grades 7 through 12. You will need both the worktext and teacher's edition for answers. There are only 15 fairly brief lessons per book, so little time is required compared to books like Wordly Wise. Saving time means that students receive minimal practice actually working with the vocabulary words.
According to the BJU Press catalog, new words are taught "...primarily through context. Students learn about word parts (prefixes, roots, and suffixes), word families, synonyms, antonyms, homonyms, and methods of word formation. The study of word parts helps students learn spelling as well as meaning. Some lessons also contain helpful spelling principles.
Books A through C concentrate on Latin word parts along with more common vocabulary topics. Book D teaches Greek word parts; Book E covers words originating from French along with some Greek and Latin words; and, Book F broadens to cover words from many languages.
Many lessons are designed around one or more word parts (with all vocabulary words derived from them), while others might center around topics such as synonyms, antonyms, a particular subject, or a literary selection. Lessons sometimes crossover to include grammar and writing skills.
The format is more interesting than that of many vocabulary workbooks because of the background information and applications in the lessons. Christian content is another plus.
You might also use the words in each lesson as spelling words rather than using a separate spelling program.
Levels A through C are suggested for grades 7 through 9. Levels A and B can be interchanged. Level D should be used after Level C, generally for 10th grade. Levels E and F are suggested for grades 11 and 12 and might interchanged. Students might complete either one or two of these books per school year.