Kids' creativity, as measured by the most recent Torrance Tests of Creative Thinking scores, has been sliding since 1990, most noticeably among our younger students. Reduced music and arts education is cited as a key factor.
I like to use the 'demolition grade' blades. They ll cut wood, metal, plaster, wire, or pretty much anything you d care to throw at them. They're made from decent carbon steel that will take and hold an edge rather well. When bought in packs of a dozen, they can be had for about a buck each.
Make the mower blade the same way as those handy self-sharpening knives. The more grass, dirt, rocks and cats you mow over the sharper the blade gets. Self sharpening blades are typically made by applying a coating or heat treatment to only one side of a blade making that side extremely hard and brittle so that chips and wear to the edge result in a new edge, just as sharp. But such a treatment for mower blades might make them overall too brittle to be practical.