I am the King of Rome, and above grammar.
-- Sigismund, Holy Roman Emperor from 1433 until 1437
I happened upon a thorough and well-done grammar website I wanted to share with you. Daily Grammar, which describes itself as "a great teaching tool for both public and home-schooled children, ESL students, and anyone needing to refresh English grammar skills," offers 440 free lessons and 88 associated quizzes. Click on the Archives button at the top of the page to access the lessons.
The Archives are very simple to use. Lessons are arranged in two ways: by number, e.g., "Lessons 71-75 -- Prepositions," and by subject, which functions like an index. Just click on the hyperlink of the lesson(s) you need. Each lesson comprises a blessedly brief (but not too succinct) explanation with examples and then five sentences or items in which the student identifies the part(s) of speech or part(s) of a sentence or supplies information as instructed.
Another most helpful feature is a Glossary defining grammar terms. Each definition also includes hyperlinks to that term's associated lessons.
Daily Grammar offers a workbook and ebook available for sale; however, I have found the free lessons to be more than sufficient for our grammar needs at this level.
Grammar, which knows how to control even kings.
Take that, Sigismund!