"hack" noun = tips or advice "hack" verb = apply tips or advice . It's an ugly word which came from a sense of hacking something (as in with a blunt instrument) rather than cutting accurately with an appropriate tool, somethign sharp. . In this misuse, it has retained a meaning of unusual, or unexpected. Though the tips offered are usually very obvious click bait, these days. . "Life hacks" purport to be things to change to make you life better. A "teacher hack", would presumably be an idea that makes teaching easier, or more effective in some way. An example might be a novel incentive to get students to turn up on time.

Hacks are hacking tricks - shortcuts to achieve results so much quicker and easier than normal such that people might say "Hey, that's cheating!" To elaborate: To hack, is to physically or conceptually pull a system apart in ways that it was not designed to be pulled apart. It is to physically or conceptually cut something up in inconceivable ways, either to understand its inner mechanics or as a result of understanding its inner mechanics - to then exploit its design flaws in order to "take a shortcut" and "cheat your way to victory" according to people who would cry "foul play" due to "digging under the perceived fair playing field".

it's an unusual tip for making stuff easier.