Older students do not do this. If they accidentally skip number 3, they'll write #3 under #4 and draw arrows to indicate the mistake. They'll scratch out a wrong word and move on. Unless the assignment is supposed to be a pristine final draft, they won't worry about making things so terribly neat.
Today I was covering 9th grade English (honors). One girl was complaining that another was taking too much time whiting out her mistake. She told her to scratch it out and move on. She questioned why the girl would bother, especially since the assignment was a four question response to a story that we had been reading.
So, I told the girl about my observations. I figured she was old enough. I explained that the girl must have been more mature than her classmate. That seemed to satisfy her.