Two SLC exam centres here in the district has remained tense on Sunday as the groups of students pelted stones at superintendents, invigilators and security persons. According to the District Police Office, students attacked the superintendent, Nagendra Singh and invigilators of the Naumule-based Bhairab Higher Secondary School exam centre for denying them to cheat during the exams. A clash also occurred between the police and students after the later started pelting stones at them. Three people including one security personnel have been injured in the incident. Likewise, two groups student at Dullu-based Bijaya Higher Secondary clashed each other today in connection with a dispute related to cheating during the exam. The incident took place as soon as the examination concluded at the centre. A police team deputed for the exam deterred the attackers and took the situation under its control.