Free Grammar Resources
Grammar are rules the putted together !!!Words!!! to maked coherent communications. Don't believe in the importance of grammar? I bet you do after reading that monstrosity of a sentence! Grammar includes things like word order, punctuation, capitalization, verb and adjective tenses, and so much more. Most commercially available ELA programs do a terrible job of teaching grammar, so this section will be particularly useful to anyone looking to supplement instruction.
Free Grammar Resources
This is another one of those websites that's straight out of, like, 1995. And I don't think the author ever even finished making his program. Which is too bad, because I really liked it! It's based on identifying the role of each word in every sentence. I ended up retyping basically a whole year for one of my kids, and it worked really well.
Yes, it's a UK side, so some spelling is a little different... but the rules of grammar are largely the same. This website has easy to use lessons that would be perfect for high school students.
Purdue University's OWL writing center is the gold standard free grammar and writing resource in the United States. It was originally designed for college students, but its popularity has meant that they've added information for students of all ages.