I don't have a suggestion about a particular drying rack model,
because I have always had to use whatever rack was already in the
different classrooms I've had, and inevitably these have been fairly
narrow and non-supportive. To avoid art drooping or falling through,
I use cardboard. I have a box of flat sheets of cardboard cut to
about 18X24 inch pieces, and the kids put their art on a cardboard to
support it in the rack, which makes any rack work equally well for me.