I myself have a Versa Laser cutter and two small Techno Davinci Mills. Small Cheap. Classroom friendly. The laser I have was working great. I cut wood, I cut acrylic, then I just lost the carbon filter and it will cost $300 to replace.
The mill I have is cheap and versitile. My kids can design on Rhino, import to Mastercam and cut away. I can also cut wood and acrltlic (in addition to aluminum). It just takes time and a lot of passesm where the laser is quick. But the mill is 10K as opposed to the cost of a laser (30K?)
Let's look at your kids and the type of projects you want to do. Also, what is your cost range? I am from Miami Dade schools, so we are a pretty big disctrict..but most of the teachers here have small Techno mills.
What is it you want to do with your kids. Intro to manufacturing? Robotics?