I tell all of my classes they can come to me for help any day during break, most days during acceleration period, and some days after school if scheduled. I can also help before school on the Tuesday mornings when I have Early Morning Detention, if scheduled by student. I am not available to "reteach" any lessons. Anyone coming for help needs to have: 1) Specific questions to ask, or 2) Problems they've tried on paper that I can check and tell them what they did right or wrong.
I do not give "extra credit" assignments. I do not feel that me taking extra time to check a bunch of busy work has any bearing on whether or not the student learned the material they were required to learn within the time frame they were required to learn it. I do allow students to turn in most regular credit assignments late for partial credit. I also provide time during and outside of class to answer any questions students may have to clarify material covered in class.