There is a system of compartments in the respective boards (ICSE, CBSE, State Board, etc.) for the students who fail their board exams. Once the results are declared, the students failing the exam can re-appear in utmost 2 papers in the compartment exams. The syllabus will be the same as your board syllabus. One must prepare well for the exam and try clearing it in the same year only. Or you will end up losing your one year. If you pass the exam, you will get the board results as passed in the same year. However, if you fail in the compartment as well, you will have to reappear for the exam in the next academic year.