I went to a second-tier (i.e., good) school and now I'm a professor at a lower level school. I assigned the same homework and used many of the same test questions as when I was a student, so the level of work was the same for the students. However, they performed poorly compared to my class back when I was a student so I had to curve the grades.
From what I've seen, professors try to cover the same material at lower level schools, but they have to curve more than they would with better students. Thus, an A definitely has a different meaning depending on the school.
On the other hand, my professor told me that at Harvey Mudd he had the same homework assigments that he gave us, except they covered the material more quickly and did more assignments. So in some cases you could find that there is indeed more work at a top level school.