This is one of those ideas that come about with the best of intentions but totally miss the mark. Most young writers do use far too many exclamation marks. Of course, there are no such things as hard and fast rules in writing, but like swearing, exclamation marks are generally much more effective if used sparingly and pointedly. So I can absolutely understand an urge to cut down on exclamation mark confetti.
However, there are two big problems here - the age and the criteria. Whether or not you approve of testing 7-year-olds (I can see a point of doing it as a benchmark), it sounds too young to pin down punctuation. Far worse, though, are those criteria.
Along with almost everyone writing since 1920, I would hardly ever use an exclamation mark in a sentence beginning 'How' or 'What'. I just don't feel the urge to write 'How do you do!' or 'What ho, Jeeves!' Checking the nearest English usage guide (Swan, Practical English Usage), there are some sensible examples for how and what, but Swan also points out that these are often formal or old fashioned, such as 'How nice!' or 'What a rude man!' And he lists various other common forms of acceptable exclamation, such as so/such sentences and negative questions ('Isn't it beautiful!')
As for 'the syntax of an exclamation'? What is that all about? Really. I have no clue what they mean. And I'm supposed to be a writer.