do most/all teachers know about 420?

Probably
As a high schooler (senior, yes I'm 18) I'd say how the fuck would anyone in high school not know?
I'd be surprised to hear about teachers smoking (at least during the school year), partly because I know in my school system the drug test. I think my sophomore civics and econ teacher probably smokes, he just fits the bill. He was fucking cool, I never did shit in his class and still made like a 98 because it was easy and we were cool.

 

now i know where i'm going for my honeymoon...

 

please be my ap chem teacher!

 

dude, same thing here i always felt like my economics teacher blazed

 

oh man, trust me they know. the vice principal and the hall monitor/detention guy would each take turns in the morning and lunch breaks at my highschool, every other day we would smoke up, but they would only leave for about 2 min then another would come, hardly enough time to get fucked, my step bro and his friends got busted smoking weed in the bush behind my school, even after the early morning anouncements that day said that its off bounds and they will be monitoring it, dumbasses

 

every day is 4/20 in my school and i make sure every teacher knows

 

exactly...hopefully my wife will be a toker too

 

They ALL know.

 

I'm sure the majority of them would know, especially in the suburbs.
However, looking back on the teachers I had, I doubt they would all be cool with it.
Perhaps the food and nutrition teachers...