What happens if we forget to submit the answer sheet for the board?
TL/DR: The invigilators will not allow any students to leave the exam hall until they have collected all the outstanding answer sheets that are still with some of the students. In any exam these days, it is a standard procedure for the invigilators to count the number of answer sheets collected after the exam to ensure it matches the number students taking the exam. That way, it ensures that they know they have collected all the answers sheets from every student. Either way, most exams will not allow you to leave the hall with the exam answer sheet because it is considered property of the examination board and no one is allowed to personally have it. So even if you forget to hand in the answer sheet, the invigilators will make sure you cant keep it and will return to collect it from you. If it is found that the number of answer sheets collected and the number of students taking the exam do not match, the invigilators will start patrolling around the examination hall to see if they have dropped any answer sheets. If the missing answer sheets are still not found, then they will likely use the names on the collected answer and compare with the students attendance one by one to find out who has not handed in the answer sheet. In short, the invigilators always make sure that all the answers sheets are collected before they can allow the students to leave the exam hall.