Quote Originally Posted by Paperplane
I was discounting this on the grounds that not all the выпускники школ could possibly have passed their exams. Am I still misunderstanding something here or are we now talking about a particular group (the ones who passed their exams or perhaps say the выпускники in a particular family who all got certificates)?
When both "сдавали" and "получали" are applied to the students simultaneously then all these students have passed their exams successfully. Since to get ("получить") the certificate one need to pass the exam.

But if we used only one verb "сдавать/сдать" we would have two possibilities:
Выпускники сдали экзамены. Students have passed their exams successfully.
Выпускники сдавали экзамены. Students tried to pass their exams. Here it is not clear whether they succeeded or not.