With my art classes, I have to give more time for the high school students than the elementary students.
high school students will spend much more time getting things accurate and perfecting every little detail. Independant art projects will take them a month.
The elementary students have limited skills and attention span. They will finish the same project in less than a week. They just don't spend the same amount of thought, nor are their standards as high. They just want to get it done, and the lack the attention to detail to really get into the project.
On the other hand, I have to prepare more specific instructions, visual aids, and guided lessons for the younger classes. If it's not written on the board somewhere the students won't do it.
The high school classes can look at a finished example and start working with some minimal instruction. Once they're working independantly then I can go around and give them individual help.