You're pretty much expected to have the grammar down by high school, where the focus shifts to composition (essay courses, etc.)
This was my experience growing up here anyways. The last time I had a test question ask me to circle the past participle was middle school (and the SAT).
I didn't know terms like that in England in the 2000s, though I picked them up from learning other foreign languages later.
I have heard university professors complain that they can say, simply, "rephrase the paper into the active voice" to a student from <anywhere else>, but many British students don't know what that means.
England now teaches more grammar, but it is not much use generalizing from individual experiences of a particular state/country in a particular decade.
YMMV; curricula are highly local.
Regarding your example with the gerund, yes it is subtle, but similar subtleties exist in German, e.g. The difference between perfect and simple past (also exist in English), which many native speakers in both English and German get wrong as well.
An interesting anecdote (which might be related) is, that in my experience having gone to high-school in the US for a year and having done language courses with Australian teachers, that there seems to be much less education on the grammar of the language than in Germany. I often knew the "theory" of English grammar much better than the native speakers (doesn't mean I was better at applying it though).
All that said, mastering English is still difficult, just not due to the grammar. Spelling is one thing, but also the vocabulary is huge. Supposedly Shakespeares vocabulary was 60000 words, the equivalent German poet Goethes was less than 40000.