Degrassi: The Next Generation & Degrassi
First seen in the episode The Mating Game, he is the teacher of a health class, to which Dr. Sally (the sexual education expert) was a guest speaker. Despite the eighth grade's immaturity and tendency to break into laughter during the lecture, they did, however, learn from it (especially Ashley Kerwin) and let it influence their decisions. When Degrassi's basketball team started their season in 2001, Armstrong had to make the difficult decision of who made it on the team. Approached with 15 hopefuls but only 12 slots, he based his team choices off the players' performances during their exhibition match against Earl Grey.With this placing more pressure on the players, Jimmy Brooks would eventually be unable to cope with juggling basketball and Ms. Kwan's English assignments. This would later cause Jimmy to take Spinner's ritalin for the exhibition game, and thus, cause irrational and erratic behavior in the two (as Jimmy experienced the reverse affects of ritalin on a "normal" brain, and Spinner was left without his medication). During the game, Jimmy pushes Sean (his own teammate) to take the ball from him, and score the winning shot. It is this which causes Armstrong to cut Jimmy from the team, saying that though Jimmy did achieve accomplishments in terms of scoring, he "show-boated, ball-hogged, blew plays, and wasn't a team player".
However, the factor that worried him the most would have been Jimmy hurting Sean Cameron, almost breaking his ankle. Despite Jimmy's protests that it was an accident, Armstrong remained committed that Jimmy had fouled Sean deliberately and that he couldn't take that risk again. He subsequently cut Jimmy Brooks. Later in the season, Emma Nelson claims that Armstrong and Liberty Van Zandt "close" because she saw them together with Armstrong rubbing Liberty's back. She later finds out that Armstrong was just helping Liberty with math. When Dr. Sally can't make it to the annual Grade 8 Sex Ed lesson, Mr. Armstrong has to take over. J.T. Yorke accidentally shot a condom onto his back without him knowing.
He found a vibrator in Clare's backpack and makes her go to the office to confront everyone about it.
Mr. Armstrong is seen teaching and such throughout the season, making remarks and what not. He is the math teacher and coach for Degrassi.
In In Your Eyes, he has a bigger role because he feels since K.C. has cheated off the exam, he will be in serious trouble. Mr. Armstrong also didn't want to see one of his best players being sucked into all of this drama that high school brings.
He is seen in almost every episode, and is giving comments, advice, and teaching throughout the season.
In 99 Problems (1), Drew and Riley are on exercise bikes and racingg to see who could burn more weight and when they finish Coach Armstrong is impressed by Riley and says he has a good shot at Quarter Back. He also has to check with Mr. Simpson about letting them have a barbeque for the football team in the parking lot of Degrassi.
In 99 Problems (2), It begins with Drew walking towards Degrassi. Riley and Owen catch him and eventually get him tied to the flagpole naked, where the other students laugh at him. Drew's mother goes to Mr. Simpson and Coach Armstrong about this, and is evidently outraged. Later, Riley tells Mr. Armstrong that he should consider Drew for QB1 as opposed to himself, but Mr. Armstrong tells Riley that he is simply better and must choose him. During the announcements of the team roles, it is revealed that K.C. and Zane are both major players. Riley is the star quarter back, which angers Drew. Drew's mother speaks to Mr. Armstrong again, and Drew says that if he can't play, no one can. As the team arrives, Mr. Armstrong gets a phone call, and announces that the team cannot play.
In Better Off Alone (2), the episode starts out with K.C., Bianca, and Fitz in a car drunk and hungover. Jenna, then approaches and talks to K.C. about his mom. During football practice, K.C. tackles the line backer which is not allowed during practice. Coach Armstrong asks K.C. if anything is wrong and if he needs anything, K.C. knows where to find him. K.C. needs references about staying at the group home. He goes to coach for help to which he says no. K.C. freaks out and without thinking, keys his car. K.C. tries to get Jenna to leave the school before he gets in trouble for keying Coach Armstrong's car, but he utterly fails and gets pulled into the office. His mother, social worker, coach, and principal talk to him. When everyone jumps to conclusions assuming that K.C. did everything, his mother (Lisa) stands up for her son and K.C. is impressed. Lisa is sick of being hurt so she tells him that he can decide and if K.C. wants to stay at the group home, she'll acknowledge his decision. K.C. appears in his mother's apartment and this surprises her. K.C. has decided to live with his mom. After saying they missed each other, they share a beautiful, memorable moment.
In Come As You Are (2), he is seen teaching Pre-Calculus, which Drew and Katie are in.
In Never Ever (2), he is seen telling Eli Goldsworthy and Imogen Moreno that they can't be excused to work on the play because it is a quiz day. He later sends Imogen to Simpson's office when she hits Marisol Lewis with her textbook.
In Doll Parts (1), he leads tryouts for the volleyball team. He gives Adam a permission form for Audra to sign, so that Adam could be on the team.
In Doll Parts (2), he congratulates everyone who made the boys senior volleyball team. He helps out Adam when he is struck in the hall with a volleyball.
In You Oughta Know, he leads tryouts for the basketball team.
In Walking in My Shoes, he hands back papers and announces to Frankie and Lola's class that they will have a test in the next class. During the test, Frankie decides to copy off of Lola. Mr. Armstrong confronts them on this since they both had the exact same answers, and he would fail them both until someone confessed. Frankie later confesses that she cheated, and Mr. Armstrong fails her test, though promises not to call her parents.
Degrassi: Next Class
In #SinceWeBeinHonest, he breaks up the fight between Zig and Hunter in the bathroom.
In #SorryNotSorry, Hunter and Yael turn their tests into him.
In #SquadGoals, he breaks up a fight between Shay and Frankie, and tells them to go work it out in the locker room.
- He has appeared in 80 episodes.
- He has been a recurring character for the entirety of Degrassi: The Next Generation and continues to recur in Degrassi: Next Class.
- Mr. Armstrong was the first of six teachers in DTNG who were rumoured to have sexually abused/harassed a student, although he was innocent. The second was Matt Oleander (guilty - had a relationship with Paige), third was Archie Simpson (innocent - accused by Darcy), the fourth Coach Carson (guilty - he made K.C. watch porn and tried to make him have sex with a hooker against his will), the fifth Winnie Oh (guilty - she had a relationship with Sav), and the sixth Grant Yates (guilty - he statutorily raped Tristan and attempted to grope Winston).
- He has been teaching at Degrassi Community School for 16 years (2001-present).
- He was a mentor for both Liberty and Riley Stavros.
- He, Dom Perino and Archie Simpson are the longest running faculty members that are still on the series.
- In Hot for Teacher, it was revealed that he is married.
- Mr. Armstrong is the longest running character in Degrassi history who has never been a regular character.
- Along with Archie Simpson, Emma Nelson, Manny Santos, Spinner Mason, Liberty Van Zandt, Christine Nelson and Laura Kwan, he is one of only eight characters to appear in all of the first nine seasons of Degrassi: The Next Generation.
- He and Archie Simpson are the only characters to appear in every season of Degrassi: The Next Generation / Degrassi / Degrassi: Next Class.
- As seen in Better Off Alone (2), his license plate was "COACH001."