HSC students who on Monday gave their computer science exams, which is part of vocational courses paper II, said there were mistakes in at least four questions in the paper.
Around 9,000 students from Mumbai division appeared for the computer science (D9) paper.
Students said four questions carrying a total of four marks were incorrect. In one of the questions, students were asked to define 'STD' instead of 'STC', which is a computer instruction.
"I was stumped to see this question. At first, I thought I had forgotten to study something and I wasted time thinking about it. After a few minutes, I realised it could be a printing mistake. When we asked the supervisors, they were also not able to help us," said Vicky Kumar, a student from Elphinstone College.
Students who want to pursue courses such as engineering opt for vocational subjects as they can deliver high scores. Students are worried that if the mistakes are not rectified, they will lose out on marks.
Suraj Sharma, a student from Vile Parle who appeared for the paper, said: "Of the 100-mark paper, I was not able to attempt four marks. Every mark counts as I want to get admission in a good engineering college."
After the exam, the education board's helpline received hundreds of calls from frantic students complaining that it was a tough paper.
A counsellor on duty at the board helpline said: "Many students called in to say there were mistakes in the paper, especially with two objective-type questions and two definitions."
"Students will have to wait till the education board issues clarification on the questions," he added.
Laxmikant Pandey, chairperson of the state board, Mumbai division, said: "After every paper, there are meetings of moderators and experts to discuss it. If they find that there were mistakes [in the questions], the state board will give the necessary concession to students in the form of grace marks."