tense agreement is highly important subject in adverbial clauses.
when ı was a student at high school, we could make a comprehensive research on the mammals.
that clause is correct. but in time clauses, reason-effect clauses and contrast clauses don't need tense agreement every time.
Although you are a member of this assosication, you were dismayed or fired by council yesterday.
As you didn't call me before, we can't participate in the meeting on time.