It makes little difference at 3.5 feet. I've worked in two offices like that; you might as well not have any walls at all because you can still see and talk to everyone around you. I don't see the point in even having such walls, except probably to use as structural support for the desktop surfaces. The only advantage they have is that they don't need legs like a standard fold-up table: those legs take up space under the table and you can bump your legs into them.

3.5 feet is barely higher than a desk (a normal one). That's like leaving your waiter a penny tip.