Also be sure you are not using “I forgot,” with him or others in the family over things they thought you were going to do. Remembering is a part of caring, respecting each other, and living in a family.
The next step is to be sure your child understands what you expect. When you ask her to do something, have her repeat your request and briefly tell you how she will go about doing whatever it was. Take five minutes for her to explain her homework assignments and describe how she will do them. She might tell you, “I will start on page 144 and read to the end of page 147. Also I will work the nine problems on page 201.” Be sure she knows what to do before you expect her to remember to do it.
The next step if the first ones do not work is to set some clear consequences for not remembering. You might say, “You forget to do your home work a lot. I also know you often forget to clean your room. You say they are important but you do not act like they are. I want to make them a little more important. Here is how I am going to do it. You will work on organizing and scheduling things. You and I are then going to figure out what will happen each time you forget to do your homework or clean your room. There need to be consequences. What should they be? If you cannot decide together, I will decide for you. What do you think?”
Positive consequences for remembering are a good idea if you can come up with them. If you use a negative consequence, be careful. It needs to be mild. Help your child remember and not to punish her for forgetting. It also needs to be something you can do daily if necessary and something you will remember. Your forgetting would itself be a problem.