So was I (and english was one of my better subjects at school).
Btw
"No person is promoted to the next higher class unless first he passes that final exam"
Completely false. No one is allowed to study for a higher qualification in a subject unless they achieve an acceptable grade in the preceding qualification. The exams for these qualifications however only occur at age 16 (GCSE) and 18 (A Level). A student can completely fail one of their GCSE's and it does not prevent them from going to the next class to study for A levels in other subjects.
There are no final exams in any subject between age 5 and 15.
"I have seen huge teenage boys in the lower grades in primary schools"
So have I, but physical size is not correlated with academic achievement. I was 6 foot tall by the time I left school, but I did well in all my exams (Barring French which I never liked and didnt see the point of).
So we can add the British educational system to the list of things that you don't know much about.
And you are still wrong about there being any contradiction in my statement.
"Coelacanth is not a species" does mean that coelacanth is not a single species. Because "a" is singular when used before a noun, it is synonymous with "one" in this usage. Do you use "I saw a bird" to mean you saw more than one bird? No, you use it to mean you saw one bird.
Definition of the word "a".
1. Used before nouns and noun phrases that denote a
single but unspecified person or thing:
It could be rewritten as "Coelacanth is the name for many species" or "Coelacanth is not one species" without changing its meaning in any way. The start of the second sentence reinforces the meaning of "a" to mean single or one by making it clear that the noun Coelacanth applies to an order.
Saying "Coelacanth is an order of fish and not a species" would also have an identical meaning. And this amply demonstrates your misunderstanding of the 2 sentences.
As there are more than one species within the order commonly named Coelacanth the noun Coelacanth can not in any way be "a species" as the name applies to more than 1 species.
It is just as accurate as saying
"Ford is not a model of car, however there are a number of models of car that are Fords".
Is there a "teaching basic english grammar" section of this forum.