I Used to Know That

rule with so many variations and exceptions can barely be called a rule. If you are in doubt go to a dictionary.

to be read to out of up for

Never use a preposition to end a sentence with

Irregular verbs just have to be learnt – sorry, learned

When adjectives are treated as collective nouns – the needy, the unemployed, the good, the wealthy – they are always plural:
The unemployed are mostly young and homeless.

There is no hard-and-fast rule

Are you red hot on the use of the subjunctive? Is it your second nature never to use a preposition at the end of a sentence?

It means simply one form of a verb that acts as a noun (there are others).

a covey of grouse
a flock of birds
a herd of cattle
a pod of dolphins

In British English, collective nouns are usually singular if the ‘collective’ is being thought of as a unit: