I bought this toy for the "big boy" in my life--my husband! He loves to build and keep his hands busy. He plays with these at his desk while he waits on computer codes and programs to install.
Magnetix toys are simply a set of magnets. They come in two shapes: round ball-bearings, and small, inch-long cylinders. Every piece is magnetic, so the pieces "snap" together in a multitude of patterns and shapes. Typically, the cylinders form the main shape of the design, while the ball-bearings act as connectors and joints.
I think these toys could be of great value to teachers as the parts can come together to create anything from basic geometrical shapes, to complex atomic models! This toy is really only limited by the builder's imagination.
The biggest draw-back to this toy is the small pieces. Obviously, this presents a choking hazard. I would be warry even of giving this to an older child who had little siblings, because the tiny pieces can easily be lost and found again by a toddler. The box recommends this toy for ages 4 and up, but I think I would recommend it for older--perhaps 8 and up. In the hands of anyone younger, the pieces are bound to become lost, and honestly, lego or megablocks will probably be more fun.