Let me explain how it works:
1. Someone does their homework:
2. Classmate copies because they didn't do it.
3. More desperate classmates come.
You'll see it more as you advance in High School. Probably not at the start of 10th Grade, but as things become more difficult and require work, people stop doing them.
Throughout my education, this only ever happened when there were easy homeworks.
If it was a short homework, or something that can very be quickly copied over (like maths), then the few people who were either pre-occupied (read:lazy) or forgot, would occassionally ask.
Most people did their work.
And in College (Which I think is equal to your High School?), there was never any copying unless it was a really simple homework forgotten.
Because usually, if you couldn't do the homework, then you probably needed help from the teacher. And if you don't make the time to do most homeworks, you're not gonna do brilliantly.
It was never a case of someone doing homework and then others copying, but more, someone does the homework, and others come along and go through it with them, or everyone does their homework together.