In kindergarten I was busy eating my boogers and crying

High-school math teacher was always sneaking off to the bathroom for a snort of vodka.

If I were a teacher I'd be boozing, too. Christ.

Fucking kids.

Guy I used to party with was a high school teacher at the time. After particularly long nights during the week he'd go into work and have a "movie day".

I had a teacher who showed up high as shit on pills, and did pills in class. She was a nut, and got fired a year after I had her. Bitch.

History teacher/asst. football coach. The ol whiskey in the mug trick.
Finally got fired after going on a bender all day at school-literally slurring by the end of the day and then went on a drunken rage at the football game later that night.
It wasnt much of a secret, almost every student had him their freshman year and almost every student sniffed his cup while he was out of the room.

My biochem teacher was always gas'd up on vodka. Still a hell of a professor and a great mentor despite being drunk half the time lol.

HS English teacher.  He was one of the most intelligent and well-read individuals I ever met.  I always wondered why he wasted his time teaching High School.  Well, turns out he was also a pretty hard-core drinking man and the teacher gig allowed for him to pursue his real passion in life.  He looked a lot like the Smoking Man from the X Files.  

If I did, they hid it well.

I can't think of any I could prove. I had my suspicions with a couple of them in hindsight.

High school shop teacher had a custom blend of tobacco he would pack into his pipe.  

Yes, he smoked in class.

10th grade (back in the early '80s), ceramics class (worthless elective I chose just to kill time during the day). The dude was always stepping out of the classroom for 10 or 15 seconds while we were working, just long enough to take a swig from the flask he kept in his pocket.

I am a teacher and some days the little fuckers drive you to drink.
I wait till I get home though. However, I am still young and full of optimism. I can see how the older ones with tenure who don't give a fuck could.

7th Grade - Had an English teach that would always hit the bottle before class began or be plastered from the night before. Mondays during the summer she would show up covered in sand and reeking of booze. Apparently on Sunday she would hit a club called "Surf Club (NJ)" on the beach. The place was open from 10:30 am to 1:30 am. I didn't connect the dots at the time, but when I was 20 I was a bouncer at the club. Recognized her right away and through her out plenty of times for being too drunk and taking dives into the sand.

College - Criminal Justice Professor - When I turned 21 I would go to the bar to grab lunch and a few beers before class since I had a 2 hour gap in between. Walked into the bar and sat down, was completely empty at that time. About 20 minutes later my professor walked in and sat next to me. Never in my life have a had that happen, thought I was going to get failed for that class and thrown out (Catholic College with a strict alcohol policy). Asked me what I was having and said just 1 or 2 beers. Told me "Beer is for pussies, I'll order the good shit." What I thought was just ordinary rum was actually 151. Seemed like endless shots, class seemed like it was over in a blink of an eye.

He wasn't a drunk but did drink and get high during the day. He was a  PE / wrestling coach.
He also was known to have banged some of the cheerleaders.  Overseas DOD school.

I considered myself lucky to have known him.

Freshman geography teacher.  He would sit behind his desk with his sunglasses on and not move or talk for the entire class. Sometimes we'd just watch movies, most of the time we just did whatever.  One time a guy smoked a cigarette in the back of the classroom.  All the goody-goody kids in the front row were trying to wake the teacher up and yelling "he's smoking", teacher didn't even move.
 

Don't know of any that were drunk but I do know one was a huge pothead.  He was my buddies neighbor and you could smell it when he went out to smoke.  Awesome science teacher though.

Do drunk bus drivers count?  My high school bus driver was plastered on a regular basis - passed out cold and drove down the median one morning.