Please tell me the meaning.

The core of the sentence is "I became aware that I had been to a 'comprehensive'.". The subject is "I" and the main verb is "became". A "comprehensive" is a type of state school in the UK. "It was only on meeting the rest of the group that..." explains the circumstance in which the subject first realised that he or she had attended such a school. The word "even" is inserted for emphasis, stressing

To GPY
Thank you so much. Now I understand. Please tell me more. Don’t you say “ It was only IN meeting ... ”? Do you use ON when you want to express “ While I was meeting the rest of the group, ” ?

emilkyWhich is the subject? I can’t find the verb either.
It was only on meeting the rest of the group | that I even became aware | that I had been to a “comprehensive."

There are three clauses, so there are three subjects and three verbs.

1. It - was
2. I - became

emilkyDo you use ON when you want to express “ While I was meeting the rest of the group, ” ?

"on meeting the rest of the group" is correct and means "when I met the rest of the group".

"on doing something" is a standard pattern to express that one thing happens immediately after another, often as a consequence. For example, "On entering the room, I n

I see. Thank you very much.

To CalifJim,
Thak you, CalifJim. Now I understand.