It is unclear from your question whether you can or cannot reach the power button.

All modern systems have a soft power button that does not cut the power.

However, holding the power button for 8 seconds will cause the BIOS to shut the computer down just like cutting the power.

If you cannot reach your power button, cutting the power to the system by removing the cord or flipping the switch on the power bar will work, but it's not the best thing for the hardware.

The other thing to do is put a script on both your machines calling psshutdown for the other machine, or for all the machines in the lab.

It is unclear from your question whether you can or cannot reach the power button.

All modern systems have a soft power button that does not cut the power immediately if it is pressed momentarily. That button can be optioned within Windows to initiate standby, hibernate (if enabled), or a regular OS shutdown and power off. The effect of the latter is exactly like going through the "shutdown" dialog in the OS GUI.

However, holding that power button for 4 seconds will cause an immediate power off, with no OS shutdown notification. In terms of the effect on the OS, it is similar to pulling the plug. Unlike pulling the plug, though, the power supply will continue to emit +5 standby power.

If you cannot reach your power button, cutting the power to the system by removing the cord or flipping the switch on the power bar will work, but it's not the best thing for the hardware, or for the operating system, or for running applications. There is often no harm at all... but this can't be guaranteed.

The other thing to do is put a script on both your machines calling psshutdown for the other machine, or for all the machines in the lab.