This is a fine goal. Having “someone write, say, 8 pages” is not, it’s a task, and a tedious one at that. No good writer starts with a page goal. It’s a common criticism by great writer’s of bad publishers.
Personally, my experience with page count assignments were... loose. The goal was never "write 8 pages" but "write about idea ABC" (book just read, subject we just studied). '5 pages' or 8 or whatever was a guideline, with the expectation that to get XYZ ideas across, it'll probably be around that length. If the guideline was X words or Y pages, and I got the ideas across in less (or more), but the ideas were strong, I still got a good grade. Perhaps some of that has changed, but... "write an essay about $foo", and you turn in 2 paragraphs... you'd get marked down.
Again, it's been awhile since I've been in middle/high school, so it may have changed some.
These days it’s often a word count rather than page count because page counts are too easy to game. There will be an upper and lower limit and when you submit the file, it might be rejected if your paper doesn’t meet the criteria.
This is a fine goal. Having “someone write, say, 8 pages” is not, it’s a task, and a tedious one at that. No good writer starts with a page goal. It’s a common criticism by great writer’s of bad publishers.