Dhaka Senior Judicial Magistrate Rajib Hasan recorded Jitu's statement on Wednesday under section 164 of the Code of Criminal Procedure that can be used as evidence during trial.
Police said Jitu described the motive and the incident in the statement. The court later sent him to jail.
Jitu's father Ujjal Hossain also gave a confessional statement on Tuesday. Police arrested Ujjal from Kumarkhali Upazila of Kushtia on Jun 28, a day before the Rapid Action Battalion arrested Jitu.
Both Ujjal and Jitu were placed on five-day remand each in the case in police custody.
The 19-year-old Jitu was produced before the court after the interrogation by Ashulia Police Station Sub-Inspector Emdadul Haque, the investigating officer of the case.
Utpal, a lecturer of political science, was also the chairman of the institution's disciplinary committee.
Jitu, a tenth-grader, attacked Utpal with a cricket stump at the institution on Jun 25. Utpal died in hospital two days later.
Describing the incident, Principal Saiful Hasan said the student started beating Utpal indiscriminately when the teacher was watching a cricket match.
Utpal’s brother Ashim Kumar Sarker said Utpal had corrected the attacker for sexually harassing female students. According to him, that was the reason behind the attack.
After Jitu's arrest, RAB said that Utpal had asked Jitu not to hang out with a girl of grade 11 at the institution. Jitu carried out the attack in an attempt to show heroism to that girl. The institution expelled Jitu and suspended the girl pending investigation after the incident.
The incident sparked massive outrage as locals and students staged protests demanding Jitu's arrest. They also raised questions about Jitu's age being recorded as 16 in the case.
The criminal justice system in Bangladesh requires people under the age of 18 to be tried as juveniles, leading some to wonder whether Jitu was gaining an unfair advantage by being identified as a minor.
The RAB collected his Junior Dakhil Exam Certificate, which mentions his date of birth as Jan 17, 2003, not a minor as assumed earlier. Jitu had faced many disruptions to his academic life, the RAB explained.