That teachers are having to be taught grammar is vaguely depressing.
I’m not a huge fan of grammar fascists. Correcting things like split infinitives drives me up the wall. It seems like the worst sort of combination of holier than thou preaching and ignorance. Victorian grammarians wanted to make English more like Greek or Latin (where you physically can’t split infinitives) so they imposed the same straightjacket on English. Unfortunately, in English it is very possible, and sometimes even necessary, to boldly, brashly or just healthily split the infinitive.
That said, I do think it is important to be able to write well, and grammar is part of that. To be fair to the 19th Century Grammarians, this Victorian poem looks like a useful aide for children.
Sentences start with a capital letter,
so as to make your writing better.
Use a full stop to mark the end.
It closes every sentence penned.
Insert a comma for short pauses and breaks,
And also for lists the writer makes.
Dashes – like these – are for thoughts.
They provide additional information (so do brackets, of course).
These two dots are colons: they pause to compare.
They also do this: list, explain and prepare.
The semicolon makes a break; followed by a clause.
It does the job of words that link; it’s also a short pause.
An apostrophe shows the owner of anyone’s things,
It’s quite useful for shortenings.
I’m glad! He’s mad! Don’t walk on the grass!
To show strong feelings use an exclamation mark!
A question mark follows Where? When? Why? What? and How?
Can I? Do you? Shall We? Tell us now!
"Quotation marks" enclose what is said.
Which is why they are often called "speech marks" instead.
Perhaps it might come in handy for teachers too?