I think the shooter will have the advantage over you as you try and get your lighter to work. :-0
A Taser (not a mere stun gun) or pepper spray would be better than WD40 or cans. Or making your desk into a bullet proof hidey hole - that would probably be better than all the other possibilities.
In the worst case, you can use the spray without igniting it. Aim for the eyes.
A way better thing than a stun gun would be a Sten gun.
Itās bullet-resistant. Nothing is truly bullet-proof. See the Staballoy projectiles from the A-10 Warthogās cannon. Itās also a good thing to specify the desired level of ballistic protection (according to e.g. the relevant STANAG spec, or we can maybe borrow the NIJ-0101.04 standard for body armor, though a ballistic desk is not exactly one, but I am not in the mood to look for standards for shields. Maybe later? Or somebody else? Prod?).
What about a school desk made from two plates of half-inch steel, with about an inch or two of concrete in between? The distinct advantage would be that the students couldnāt carve into the desks.
There may be some reduction of the firepower, but it still may be good.
A slo-mo shot of a wd40 fire test. Year-old video, you can compare it with your experience and see if the inert propellant worsened the performance.
Indeed, I admit my error in using a colloquialism. I bow to your ballistic pedantry. And now I live in terror of an office shooter carrying a 30 cannon terminator-style through an office thatās woefully under prepared with mere class III armored desks.