In the season premiere episode, "Unbraceable You," Frankie makes a giant blunder when she discovers that school started a week earlier than she thought, and Sue and Brick must scramble to catch up on the days they've missed and re-acclimate themselves to school life. Meanwhile, it looks like the "Year of Sue" might be starting off on a high when she finally gets her braces removed. Axl beats Mike at basketball for the first time in his life, and Brick gets creative in an attempt to find the perfect school book bag.
Frankie and Mike scramble to find second jobs in a desperate attempt to afford sending Sue to a good college next year. Sue and Brad strive to do something different and important while writing, directing and starring in the senior play, entitled "The Loneliest Locker," instead of eating the family out of house and home, Axl literally begins to take the home apart when he removes -- without asking -- as many household items as he can to furnish his and Hutch's new rented house, and Brick drives the family crazy when he finds a box containing all of his noisy and annoying childhood toys -- that were purposely stowed away by Frankie -- and begins playing with them.
In an attempt to become more social, Brick shocks Frankie and Mike by informing them that he'd like to go to his middle school's Fall Fantasy Dance, Axl begins to panic when he discovers that he needs to declare a college major by the end of the week -- and he has absolutely no idea what he wants to do, and Sue finds herself becoming a bit twitchy and nervous when she begins to drink a lot of coffee in an attempt to appear more mature and sophisticated, now that she's a high school senior.
As Frankie and Mike wish each other a happy 20-somethingth wedding anniversary, Axl decides that he and Hutch need to class up their broke-down house and find another roommate to help with expenses. But while helping Axl track down a dining room table to help spruce up his house, Frankie finds a full dining set on sale online for $50 and ends up giving Axl the Heck house dining room table, while she excitedly looks forward to her new purchase. Meanwhile, after being presented with a special necklace to proclaim his love, Sue becomes angry with her boyfriend, Darrin, when she discovers that he had also given the same gift to his former girlfriend. And Brick begins a podcast.
It's Halloween night, and Frankie and Mike are stunned - and a bit scared -- to learn that Brick has invited a girl over to the house just to hang with him. Meanwhile, to help supplement her college fund, Sue attempts to put together a pumpkin patch screening of the animated classic, "It's the Great Pumpkin, Charlie Brown," and Axl reluctantly goes to the library to write a history paper and ironically gets locked inside after staying past closing hours.
The Heck house once again throws a curve ball to the family when the kitchen sink caves in and drops out of sight, causing Frankie to have to wash the dishes with the outside hose. Meanwhile, Sue is informed that, since Wrestlerettes does not qualify for P.E. credit, she needs to master tinikling -- a difficult dance routine for a clumsy Sue -- to get the credit she needs to graduate, and after Brick accidentally breaks Mike's lawn mower, he takes Axl's advice to try and play the hero card by taking his dad's wallet then returning it later, thinking this will divert Mike's attention away from the busted mower.
The Hecks go to a restaurant buffet for Thanksgiving dinner. However, the meal doesn't go well because Sue suspects that Mike dislikes Darrin, Brick invites his unconventional girlfriend and Frankie makes Axl bring a date he doesn't even know.
Mike accompanies Sue on a college tour weekend, and Frankie abandons Brick with a school project and a revolving door of babysitters while she goes to see Axl play in his first college football game.
Frankie has had enough of schlepping out the Christmas decorations and trying to make the perfect holiday for her family -- who she feels doesn't appreciate all that she does for them -- and decides to kick back on the couch and have a minimalist Christmas this year. Meanwhile, due to Sue's allergy to real Christmas trees, Mike attempts to purchase an artificial one and ends up not getting what he paid for. Axl puts Boss Co. back into business for the holidays as Tree Wise Men but gets into such a heated argument with Sean over a misfit toy that the two can't seem to work together, and Brick becomes fascinated by a Christmas letter the family has received and attempts to write one on his own outlining the past year of the Hecks.
Frankie is thrilled when Pam Staggs - the most popular girl in high school who wouldn't give Frankie a second look back then - moves back to Orson and invites her to hang out. But Mike becomes concerned with Frankie when she and Pam begin partying every night and acting like rebellious teenagers. Meanwhile, Mike is shocked to learn that Brick has received the middle school's Athlete of the Month award; Axl tries every trick in the book to get Devin Levin to go out on a date with him, and Sue attempts to take on the oboe, rowing and raising farm animals, thinking that these obscure extracurricular activities will help her get into a good college.
Frankie discovers an old, uncashed paycheck from Ehlert Motors. But in order for her to collect her pay, Mr. Ehlert forces her to work on the lot for one day. Meanwhile, after her hours at Spudsy's are cut down, Mike offers Sue a part-time job as the quarry cleaning lady; Mike's dad, Big Mike, attempts to persuade a lazy Axl to help replace the Heck family's damaged kitchen sink, and Brick discovers the joy of watching '70s game shows and begins his own annoying classic contest with the family.
After learning that Aunt Edie has passed away, the Hecks board a train with the body to take her to her final resting place in South Dakota. But along the way, Frankie accuses Mike of not being very caring or nurturing after she trips in the dining car and is helped up by another man, while Mike continues pumping out some ketchup. Axl believes that he was responsible for Aunt Edie's death because he had used the excuse that his Aunt had passed away numerous times to get extensions on his school assignments, Sue attempts to complete her college entry essay and accidentally sends it before correcting an inappropriate sentence and Brick decides to take a risk and live outside his comfort zone by befriending a complete stranger in order to live his life as freely as his late Aunt did.
Valentine's Day aims its sights on the Heck kids when a nervous Brick finds out that his quirky girlfriend Cindy wants him to kiss her on the special day, Darrin asks Frankie and Mike to help out with an exciting scavenger hunt he's putting together for Sue, and Axl begins to question his girlfriend Devin's request that he not give her anything for what she considers to be a lame tradition.
The Heck family learns about Darrin's marriage proposal to Sue.. as well as her response. Meanwhile, Axl attempts to use his intro to Psych class to cure Brick of all of his quirks and tics.
Frankie feels nothing but guilt when she realizes that she and the family forgot to celebrate - or remember - Brick's 13th birthday, which had come and gone three months earlier; Sue goes a bit overboard in trying to establish something unique about herself in order to receive a senior superlative recognition and finally be included front and center in the school yearbook, and Devin does not like the way Axl categorizes women in his phone contacts and abruptly breaks up with him.
Frankie finds herself innocently flirting with Axl's hot friend, Finn. But when she makes a not-so-innocent remark about him to her sister, she fears that both Finn and Axl may have overheard her conversation. Meanwhile, Sue is forced to take Brick to a "Planet Nowhere" sci-fi convention, and Frankie's dad, Tag, asks Mike to secretly help him study and pass his driver's test so that he can keep his license from being taken away.
Sue tries to clear her head by making potpourri Sue-venir sachets to give away to her classmates, while Frankie is on pins and needles as they nervously wait to find out if Sue has been accepted to any of the colleges she applied to. Meanwhile, Brick kicks Axl out of the bedroom and into the dining room as he attempts to find some peace and serenity so that he can attempt to write a novel, and Mike refuses to admit that he was rocking out in his car and singing at the top of his lungs - even after his whole family witnessed him doing it.
Frankie accompanies Brick on a school field trip and attempts to help her socially inept son make friends with a couple of boys. Meanwhile, when Devin scolds Axl for being mean to his sister, he tries to make it look like they are the best of friends when Sue spends the weekend at his house; and while trying to thin out some of their hoarding father's massive stockpile of junk, Mike gets a sinking feeling that he may have bullied his brother Rusty a bit too much as kids and turned him into the hapless man that he is today.
After Axl forgets to bring home a sombrero that Sue needs for a special high school senior photo she's setting up with Brad, she becomes super angry and won't let up on arguing with him. In an attempt to remedy the situation, Frankie takes Mike's advice to individually tell Sue and Axl the truth about how she thinks each of them is handling the situation, which causes even more friction amongst the bickering siblings. Meanwhile, Mike is shocked to learn that Brick has been awarded with the middle school's Athlete of the Month award.
Case of disrespect hits the Heck boys when Axl -- who is celebrating his milestone 21st birthday -- refuses to come home and help Mike move an old freezer, and Brick begins turning into a mini-Axl by dissing Frankie with a bad attitude. Meanwhile, Sue is torn over what to do when the manager of Chop Suey USA tries to woo her away from her job at Spudsy's.
Frankie and Mike find themselves caught in the middle of a long standing family feud when Frankie's Uncle Dutch contacts her dad, Tag, in an attempt to reunite and bury the hatchet with his estranged brother. Meanwhile, a fearful Sue receives her first detention ever for being caught going off campus for lunch and seeks advice from Axl on how to survive the ordeal unscathed.
Frankie and Mike attempt to have a romantic date night at home by renting a movie. But every time they turn it on, they end up falling asleep and try desperately to get through the film over a series of nights. Meanwhile, Axl teams up with Brick to invent the next big thing, and the Heck Brothers Old-Timey Barbecue Sauce is born; and Sue is floored when she's asked to her senior prom by a hunky mall store greeter. But she has to figure out a way to get out of work early in order to attend.
Tired of getting lousy Mother's Day gifts year-after-year, Frankie informs Mike that she wants him to take her out for a proper afternoon tea. But Mike's ineptness at setting up reservations online could end in disaster. Meanwhile, Mike orders Axl, Sue and Brick to put some effort into choosing a great Mother's Day gift for Frankie; and Frankie doesn't get the answers she was expecting when she asks each of the kids what things they would do differently than her when they become parents.
As graduation approaches, Sue begins to think that "the year of Sue" may end on a sour note when a series of unforeseen events threaten to ruin her special day. Meanwhile, Frankie and Mike are stunned to learn that Brick is doing so well in middle school that he's been offered the chance to skip eighth grade and go directly into high school; and as summer vacation commences, Axl sees some images of his girlfriend Devin on social media having fun with some guys back home and begins to think he may lose her.