The new laptops have a 'feature' that they automatically detect a connected monitor and send the signal to that on startup rather than to the laptop's monitor. In our situation we have the projectors hooked up to the laptops constantly, but the majority of the time (and especially on boot) the teachers are using the laptops as a laptop, not through the projector.
Finally found a way to turn this 'feature' off:
1. Turn on computer by holding down power button while pressing the ESC key. The machine will beep, then display: Check System, then press F1
2. Release ESC key
3. Press F1 key
4. Go to the second page by pressing PageDown
5. In the Display setting, set to LCD+RGB instead of auto-select.
6 Press End to save and exit