Your friend can definitely register for CBSE improvement exams. These are called compartment or improvement examinations , conducted usually in August and results come out around October–November . He should check the official CBSE website or his school’s CBSE portal to apply online once notifications are released. If marks in one subject are low, he can retake that single subject. If overall percentage is low and he wishes to improve across subjects, he may have to repeat the full exam. Schools guide students through the registration process and help submit form and fees. Your friend should connect with his school’s CBSE coordinator to start the process as soon as the forms are available.