LanSchool Classic's 9.2 version and below requires the installer (teacher.msi) to be ran a second time. The installer must be for the same version of LanSchool that is currently installed on the device. This will require local administrator permission to install or remove software from the device.
If you have issues uninstalling LanSchool Teacher on Windows, place the installer on the Desktop of the student computer and run the file from the Desktop. When prompted to browse, browse to the location on the Desktop and then you will be able to uninstall.