Betty Schrampfer Azar's grammar charts in her Understanding and Using English Grammar: Chartbook, they are an informative, handy (and really quite amazing) language teaching and learning resource and tool, and while of course primarily conceived for ESL students, they in my opinion can and actually should be considered by and for anyone wanting or needing a user-friendly and portable reference manual for basic English grammar rules, with Schrampfer-Azar’s set-up being concise and organised, and the rules themselves also presented clearly and thankfully without over description and analysis.
And yes, and in my opinion, parents especially would do well to consider investing in Understanding and Using English Grammar: Chartbook or similar such language arts books for at home usage, as it sadly and frustratingly seems more and more the case that grammar instruction especially has fallen by the wayside so to speak for schoolchildren in both Canada and the USA (that supposedly, teachers are often actively discouraged from teaching traditional language basics and sometimes not even PERMITTED by their respective school boards to teach grammar and standard word, sentence parsing skills). But honestly, why do university and college level ESL students often receive better grammar instruction than native speakers do and why do they more often than not have better grammar and writing skills? It is to despair, but perhaps these grammar charts might aid in rectifying this educational shortcoming.
Finally, just to point out that I have in fact often used (and continue to use) Understanding and Using English Grammar: Chartbook for remedial English grammar practice/learning with my first year German language students, in order to show them the general differences between the subject, the direct object and the indirect object of a sentence (prior to for example introducing the accusative and dative cases, which in German have distinctive forms and endings). And while I am of course pretty darn annoyed and continuously frustrated that I actually have to teach remedial basic English grammar skills in my first year German courses, I now simply shrug my shoulders and reach for either Betty Schrampfer Azar's language charts or English Grammar for Students of German (as this just is what it is, and well, I do not really think that the current state of affairs of Canadian and American secondary school students often if not generally no longer being taught basic English grammar skills and syntax is likely to change all that much, all that significantly in the near future).
I'm a huge fan of Azar's grammar charts, having used several editions of her classic English grammar texts ever since I began teaching ESL in 1981. Even those who are not teaching or learning English will find her succinct approach to parsing English grammar to be enlightening. This book is essentially all the charts taken from Understanding and Using English Grammar, presented here without the accompanying exercises in that grammar text. I've at times used the grammar chartbook in combination with other non-Azar texts or referred students to it for grammar review of key structures.