Teachers should be very careful about the extra duties they take on. This is true for all teachers, but especially true for new ones.
There are enough extra duties available for teachers to keep them busy around the clock. Be careful about volunteering for too much and wearing yourself out.
Sometimes you may have no choice but to take on extra responsibilities. New teachers seem to be the first ones to get things piled on to their regular work load. This doesn't seem to make a lot of sense considering that new teachers are the ones who are still getting used to the profession.
Trying to help out and look good for the boss is not necessarily a bad idea. Just make sure that it is not at the expense of your health, mental state, and classroom performance.