Scenario: as you walk into an empty class, you see a bag on the floor under the desk what will you do next

I'm not sure on what you mean by this however lets say that it may contain a device, when entering DO NOT TOUCH ANYTHING, there are different methods on how a device could be triggered either from light switches or by trip wire which its best to leave the facility over all however lets say you cannot then stop listen for any ticking if not then have a flash light, if the room lights are turned off leave them off use a flash light but be careful where you shine it there could be light sensors on the device that trigger when a light hits it hence why the lights are off. when having a flash light you could be able to see a glare of a wire which could be a trip wire. there are many possibilities in how the device was made from timers, trip wire, sound,light,pressure, switches, electronic waves from phones may effect the device and could activate it as well. But anyways this is all a factor and its best to be careful and if able evacuate if the device is in a weird location at a odd time you know its not suppose to be there, and or items moved that are never moved and if it is never moved then there is dust that could have a odd shape like a hand print. Anyways im not sure if your looking for this type of answer but its good to know!