could anyone advise please the difference between (if any):
AFTER I had finished my school I went to Canada.
I had finished my school BEFORE I went to Canada.
AFTER I HAD FINISHED MY SCHOOL I WENT TO CANADA. (I THINK PAST PERFECT EMPASISES THAT ONE PAST ACTION CONCLUDED IN ORDER TO OPEN THE WAY FOR THE OTHER ACTION TO HAPPEN IN OTHER WORDS THE PREFERENCE OR OBLIGATION WAS TO FINISH THE SCHOOL FIRST BEFORE GOING TO CANADA).
AFTER I FINISHED MY SCHOOL I WENT TO CANADA.(MAY IMPLY MORE OF INTRODUSING FACTS OF HOW THINGS DEVELOPED)
One should be aware of the Past Perfect Tense and that is beyond any discussion. On the other hand, I barely hear native speakers using this tense in their speech. All of us know that "the Past Perfect expresses the idea that something occurred before another action in the past. It can also show that something happened before a specific time in the past."
I do think, however, that either "after" or "before" do the job as BobK's sentence shows above.
The four points raised by Banderas and the reply of David L in another thread on the same issue seem to point to something more happening here. If #2 is the reason for the past perfect, why is there sometimes the option to not use it?
And why, in the thread above, has that option seemingly disappeared?
You normally use the past simple tense with after and before when one action preceding another happens immediately or within a short time apart (it's up to the speaker what they think a short time is). Otherwise, you use the past perfect tense:
After she finished with the fruit salad, Mum started to lay the table.
After she had left university, Monica found a well-paid job in advertising.
Before Mum started to lay the table, she finished with the fruit salad.
Before Monica found a well-paid job, she had left university.
Now if you see a sentence like the above, with the past perfect simple tense used, you might well think of this idea; the author of the sentence might have had such in their mind, who knows.