def students_check_types(row: tuple) -> bool:
    """Returns true if row containing students data has correct types"""
    try:
        index = int(row[1])
        if index < 100000 or index > 999999:
            return False
    except ValueError:
        return False
    if not isinstance(row[2], str):
        return False
    if not isinstance(row[3], (str, int)):
        return False
    return True