Latin losing its place in English language

I am fighting a losing battle.  The trouble is, kids aren’t taught Latin in school anymore.  So they don’t know that for the most common gender-neutral Latin nouns, “um” is singular and “a” is plural.  And that this distinction is maintained when the nouns are imported into English.  As in:
 

• bacterium --  bacteria
• quantum – quanta
• desideratum – desiderata
• erratum – errata

 and of course

• medium – media, perhaps the most frequently occurring example of erroneous attribution of the singular to the plural form.

 Radio is a medium for communication; radio, TV and magazines collectively are media.  Marshall McLuhan wrote that “the medium is the message” intending it to be something of a conundrum, but a singular concept.
 
Not all English nouns ending in “um” are of Latin origin.  One such is “conundrum”; its plural is “conundrums”.
 
A parallel error is frequently made with Greek nouns imported into English; if there is one test or standard, it is a criterion; if there are several tests or standards, then collectively they are criteria.  But many people mistakenly say “criteria” thinking it to be singular.
 
And of course we have the pervasive problem that many of our schoolteachers don’t know these rules, and typically know no Latin nor Greek.
 
What is to be done?  Are those of us born in the 19th Century the only ones left who care?
 
Admittedly, the English language evolves.  We don’t have the equivalent of l’Acadmie Française.  But some things grate.  Among them “they”, “them” and “their” used as in the singular.  To avoid a gender connection.  What would we do if we all spoke French, where gender connections are de rigueur, as we say in English? 

The suggestion that we substitute “horshit”, for “he or she or it”, has for some reason not caught on.
 
-- Bob (born 02 July 1867, just in time to be a Canadian)
 
PS: Erratum:  Actually, it’s inconceivable (in at least two senses) that I was born in 1867.  But I still look to the writings of that era as setting the criteria for English prose and poetry.  When was the last time any of us read any Milton, Pope, or Dryden?  We seem to have a Dickens of a time harking back to those talented writers.