Encourage your child to go for excellence. Students get so hung up on page numbers: “How long does this essay HAVE to be Mrs. Atkins?” My usual response is, “As long as it needs to be. Just make it brilliant.” Focusing on quantity means they are not focusing on quality. They are strategizing to get three to five pages, not developing their ideas to address the academic question thoroughly and thoughtfully.
Often, I’ll give students a choice between two assignments. One assignment is a bit remedial, and definitely grade appropriate. The other is a little more complex, requires extra work on their part. If they choose the first, they cannot get any higher than the basic grade of “C”. It becomes a pass or fail assignment. An “A” means excellent, and you cannot give excellence when you are producing the basics. The “basics” get you a paycheck. But “excellence” gets you the promotion. There’s an important life lesson here. However, on the second assignment, the sky is the limit. Of course, I don't promise them an A but the possibility is there. And for the record, a "B" is a good grade as well!
When I hear this question of "How many pages?" I assume one of two motivations: either the student wants to know the least amount of work he has to do and/or he wants to know what he has to do to get a good grade. Either way, that student is worrying about the wrong thing. What every teacher wants, or at least should want, is a class full of students who can look themselves in the mirror and honestly say they tried their best and learned something new. A class-full of A+ students means just as much to good teachers as a class-full of D+ students, we want the same outcome = learning. An A+ student may learn nothing all year; this student has failed just the same as one who received an F.