<p>I took lots of grad school courses as an undergrad (though not in math or science). Some were taught at undergrad level as far as I could tell (i.e. the architectural history sequence which was officially a grad school course, but open to undergrads), some had slightly different requirements (i.e. a paper might be optional for undergrads and required for grads), one was more intense, but also by far and away the best course I took (Chinese Landscape Painting of the Sung Dynasty).</p>