Much harder that is, than any other subject a thirteen year old student usually was expected to comprehend ---- or ever should have been expected to comprehend.
Since 1965 was the very last year of the Age of Modernity and of Exclusion, this grammar course was in fact the last throw of the era of popular eugenics.
Grammar fears were never as much a moral panic before and after 1875-1965, as they were during it.
Intense grammar instruction grew up with 1924's Johnson-Reed Act and as just as that legislation exclude from the external borders from all foreign beings, the grammar teachers worked to exclude all foreign thoughts (from radio,comics,TV, black singers,films, Jewish comedians) from illegally crossing the internal mental borders into the brains of the nations' middle class WASP children.
Even as a kid, I could see how much more angry they were if the phrase 'ain't' dropped from the lips of those of us thought likely headed to university rather than from those of us thought headed for typing jobs and the manual trades.
They didn't seem to mind poor kids talking trash --- their trash --- they just didn't want the pure Anglo Saxon tongue to shack up with that trash talk and nine months later produce some miscegenated slangy baby.
Last of the eugenicists
The designers of these grammar courses were very smart.
They didn't really expect any student to grow up able to quickly parse a sentence and extract the past subjunctive anterior, they just wanted to bash our brains in with all these highly technical grammar terms in order to impress upon us the high importance that adults and employers gave to speaking like a BBC announcer.
Even back in Grade Three, in 1960, I was scolded so many times for insisting that those things up in the sky were 'airplanes' and not 'aeroplanes'.
Grammar teachers as eugenicists : working full out to encourage the heightened breeding of pure Anglo Saxon English and sterilize all the impure Negroid English...