Sometimes they don't even bother to walk in. Disembodied hands just reach around the corner from the other part of the shop and heave refuse into the workshop. Or someone passing by will throw or boot empty cartons, bags of garbage, or wads of plastic bags over the threshold.
This and the sounds of urination and toilet flushing from the apartment above really help me maintain my professional attitude. Try it: do whatever you do for a living while someone tosses garbage into an unruly pile next to you and someone else pisses in a bucket above your head.
Don't just stay in school, kids. Stay in through graduate school, and make sure it's in something important and lucrative. Or start a waste disposal company, so the trash IS the product. You'll have fewer student loans that way.