My district uses Computrace -- note I am a teacher tech and am not at any decision level at all, and I am relating what I've been told by the powers that be.
I've been with my district 17 years, and over the years, I've seen various lock down devices.
The first set of computers in my room were bolted to the tables with a very long bolt that had to be undone with a special device if you had to work on the hardware. I've seen computers glued to various types of lockdown pads and combinations of security chains.
All of these had some common problems -- techs had to have a special device to unlock the security devices before they could work on them, usually requiring different keys or wrenches.
BUT the computers were still stolen, often theives would take the whole table with the computer(s) and monitor(s) still attached and detach them at their leisure.
All that changed when we started issuing laptops to teachers. They all had CompuTrace installed on them and I remember one of our adminsitrations relating stories about how the laptops were found -- one even involved in a child porn case, investigators found the alleged pedophile in the hotel room where the suspect was hiding out.
All of the district computers are now protected with Computrace or the like. The laptop I am working on right now has one, and you know it when you go into the System setup -- it tells you.
Monitors are so cheap, they don't worry about their theft, they just send out new ones. We buy in bulk so get a better deal. Same with mice and keyboards.