Acting Proctor Amzad Ali said the incident occurred at around 3pm on Saturday.
The victim has been identified as Mohammad Ali, a ninth grader of Birshreshtha Motiur Rahman School in Bangshal.
Bathing in the pond was banned after a Dhaka University student drowned in it last year.
Amzad Ali said, “They (the schoolboys) bathed in the pond even after seeing the signboard forbidding everyone from bathing in it. It was very unfortunate.”
He said the two bathing-stands of the pond would be fenced off if people continued to violate the ban.
In Dinajpur, three schoolboys drowned in the river Punarbhaba at around 1:30pm, Birol Police Station Inspector Anwar Hossain said.
They have been identified as Mehedi Hasan Palash, a grade-10 student of Dinajpur High School, Abid Bin Turja, an eighth grader of Dinajpur Zilla School and Masud Abdullah, a grade-11 student of Dinajpur City College.
The police official said the trio drowned while bathing in the river.
Locals recovered the bodies since Dinajpur Fire Service does not have any diver, he added.