And it is tempting for the parent. No one wants to see their child suffer. But that little bit of siuffering will pay off big for the child. The child will gain knowledge, problem-solving skills, ethical work habits, confidence, and the satisfaction of having done the job himself (or herself). He or she will also be more likely to become an independent and self-sufficient adult.
If you really want to help your child, make sure they have a proper diet and plenty of exercise and sleep. Make sure they go to school everyday on time. Make sure they have time and a place to study each evening. Supervise their study time and help them through obstacles, but don't do the work for them.
I used to have students who would turn in papers in two different sets of handwriting. Maybe they thought I couldn't tell, but it's pretty obvious, especially when the easier problems are done in the student's handwriting and the harder ones are in someone else's.
I was reading a blog today where the parent had written the child's entire term paper and had plagiarised the whole thing. This may be one of those cases where parent and child both deserve grades lower than "F."
If, as parents, you want more information as to how best to help your child, talk to your child's teachers. They should be able to give you lots of information about the courses they teach and how your child can succeed in them.