Bangladesh has been experiencing heat waves across the country, with a high of 41.5 degrees Celsius in Chuadanga on Friday
As many as 3.23 million are taking the tests, which started on Sunday.
The Primary and Mass Education Ministry Mustafizur Rahman visited a centre at Dhaka's Agrani School and College.
Fewer candidates are taking the tests this year.
According to official figures, 3,230,288 students have registered for the examinations -- 24,266 less than last year.
The PEC test was introduced at the fifth grade in 2009 following a Cabinet decision.
Those at the eighth grade, appear in the Junior School Certificate (JSC) and Junior Dhakil Certificate exams.
Earlier, there was a separate exam at the fifth grade for scholarships, which has been now replaced by the PEC and Ebtedayee.