I have another example:
"She stared at the work piled up on the desk."
There are three ways of understanding this:
A) ...the work that had piled up on the desk.
B) ...the work that was piled up on the desk.
C) ...the work that had been piled up on the desk.
The most natural one to me is B - with 'piled up' being read as an adjective.
The quirky thing is that both A and C also seem valid; with 'piled up' in A morphing into intransitive, and in C clearly passive.

There doesn't seem to be any 'rule' here.

I was abroad not the school

@WW you're right - the sixties in London were indeed full of linguistic snobbery, but now we have a sort of 'newspeak' management and PC language instead, which in its way is just as bad.
BTW after forty years abroad my old school finally hunted me down and with dunning charm suggest a "gifting program".

https://www.mtholyoke.edu/acad/intrel/orwell46.htm

Somwhat more withy benchmarks and guidelines.

@CB and "started"? "butted"? "farted"? "matted"? "tested"? "textiles"? "contextual"?

Mostly covered at:
http://en.wikipedia.org/wiki/English_subjunctive

I think Murpy/Hewins mentions that Br English often uses "should" after a verb like "recommend", whereas apparently Am English prefers subjuctive.
Eg: "They recommended that interest rates (should) be raised".

@Brus Whilst learning Latin may be great fun, surely learning almost any inflected language would serve to raise awareness of grammar?
The other criterion would be usefulness. Clearly a smattering of Latin (and Greek) are still a prerequisite for studying western medicine, botany, European history and so forth;but for business Spanish, Japanese, Chinese or something would have more practical application.
Again, outside the catholic church, latin is dead; much easier to find teachers and watch the news in a living language.
One also needs to look at the impact of so many children using English as a second language, even in England, Speaking one language at home and using another for exams, education and business can lead to colloquial competence in the home-spoken language, but a narrow vocabulary, and vice versa for English.
Where I am living, even at secondary school, English is the medium in the classroom; but in the playground and outside children tend to separate into their own first-language groups. We have here schools where well over half the students would rarely speak any English at all over the weekend. Becoming more aware of Latin grammar (well any grammar) might indeed help a little, but hardly a cure-all.
There is a real difficulty in acquiring a university/business level of English with so many opaque latinate borrowings endemic. For instance, the links between "correct", "director", "erect", "regal", and "real" are obscure in English. The wordoots in some other languages ( say, German) are often more obvious.

@Brus Wow thanks - and I thought 'rectum' meant 'anus' as in 'anus horribilis'.

Speaking as a leftie, if one wishes to learn a language, the earlier one starts, the better. So shouldn't we all be learning and using Latin as soon as we start primary schooling? All we need is teachers who speak latin fluently. Then we could speak English proper.

@WW "By far the biggest problem, at every level I'd say, is will and would after if."
And amen to that - at least for Eurolanguage speakers.
For non-Euros one needs "Learner English" Swan CUP. a mine of useful stuff.