Ward and June are concerned when they discover that Beaver's visiting friend Chopper has divorced parents but soon see that Chopper's own experience will serve as Beaver's best lesson on this life changing event.
Beaver's slightly exaggerated story about rescuing an abandoned canoe while fishing with Wally takes on a life of its own while passing through the school grapevine and Beaver finds that not being completely truthful can have disastrous results.
Beaver proudly takes his friends Whitey and Gilbert on a picnic at the lake to see Wally in his first day as a lifeguard, not knowing that a new law forbidding anyone under age 18 from filling the position has forced Wally to work as a snack vendor instead. When he sees Wally in a floppy hat peddling hot dogs instead of sitting importantly on a stand in a lifeguard uniform, an embarrassed Beaver wants to go home before anyone else finds out.
Lumpy Rutherford embarrasses Beaver, calling him 'Freckles' in front of his friends and Beaver tries various ways to get rid of the offending spots. While Ward and June try to convince their son that what's important is not what he looks like but what kind of person he is, in the end, Beaver finds his own support from an unlikely place.
Beaver sells raffle tickets to benefit the new hospital and hopes that one of his own will win him a Hawaiian vacation or a sports car. When obnoxious Eddie Haskell teases that Beaver's parents would never allow him to keep a top prize and would most likely use it themselves, Beaver refuses to believe. But when one of Beaver's tickets is a winner will Eddie's dire prediction come true?
Eddie Haskell boasts about going steady with popular Caroline Shuster but Wally hears Caroline tell her girlfriends that she thinks Eddie is a creep and must decide how to break the bad news to his best friend.
Ward is concerned that Beaver's attitude toward his schoolwork will jeopardize his future and when the school principal announces that Beaver's class will be given an intelligence test Beaver worries that the results of the test will not only prove his father right but show that he's too 'dumb' to succeed.
To impress pretty, out-of town girl Kitty, Wally writes letters to her exaggerating his family's wealth and importance; but he must later eat his words when Ward and June tell Wally that he will be taking Kitty to the country club dance.
Ward and June leave Wally in charge at home and all is well until neighbor Mrs. Murdock drops by and asks Wally to take her son, Chuckie, to buy new shoes. But Wally goes ice skating with Eddie Haskell instead and turns little Chuckie over to Beaver. When Beaver loses Chuckie in the shoe store, Wally soon learns an important lesson in responsibility.
June attends a meeting at Beaver's school where teacher Miss Landers confides that several items have recently disappeared from student lockers; and when June finds the same items under Beaver's bed she worries that Beaver may be the thief. Ward questions Beaver and finds out that Beaver was given the items by another boy, Kenneth, but Kenneth denies everything and Beaver must find out why.
While emptying the trash, Beaver finds a circular that Ward discarded offering a free trial for an expensive new accordion. With a push from troublemaker Eddie, Beaver secretly sends in the order form, believing that he can play with the instrument and return it within the 5-day free trial period. But, as usual, things don't always go as planned.
When Wally starts dating Julie Foster, the daughter of a teacher, Lumpy and Eddie tease that Wally is only seeing her to curry favor with her father, especially when Wally is later assigned to Mr. Foster's English class.
When Beaver decides to be a writer, Ward gives him a diary, encouraging him to write down his thoughts and daily activities and assuring Beaver that no one would read it without permission. But when Beaver is late coming home one night his worried parents break the lock on his diary, hoping to find a clue to where he might be and, instead, getting quite a surprise.
After being warned against roughhousing by the track coach, Eddie and Lumpy start a towel fight in the school locker room and the coach walks in just as Wally throws a towel. But when the other boys deny any wrongdoing, Wally takes the punishment alone and must tell his parents that he is suspended from the upcoming track meet that the whole family planned to attend.
Jackie, a friend from Beaver's old neighborhood, comes for a week-end visit and the excited boys look forward to the fun of playing the same games they used to play years before. But Beaver and Jackie soon find that their interests changed as they each grew older and the week-end doesn't turn out quite like they planned.
Beaver loses his fear of a possible operation to remove his swollen tonsils when Ward reminisces about his own boyhood tonsillectomy. In fact, Beaver is so impressed by Ward's story of ice cream, pretty nurses and gifts that he can't wait to have the operation himself...even if he doesn't need it!
When the local pet store has a tropical fish counting contest with a collie pup as the grand prize, Beaver and his friend Gilbert agree to enter together and share the puppy if they win. But slick Eddie Haskell starts working at the pet store and claims to know the winning number...will Beaver want to win badly enough to cheat?
After finding Ward's old drawing tablet, Beaver volunteers to make a poster for a class project on Colonial America, hoping that his talented dad will do it for him. But Ward only offers his son advice and encouragement and, even though his friends make fun of his art, in the end, Beaver is glad that he painted the poster by himself.
When the Cleaver's former housekeeper, Mrs. Manners, is unavailable she sends her teenage daughter Margie to help June part-time after school. Ward is amused when smitten Wally skips track practice to spend time 'helping' pretty Margie but June worries when Wally neglects his homework.
Lumpy and Eddie try to sabotage Wally's efforts to help new kid Dudley fit in with the school crowd but, when they invite Dudley to a popular girl's party just to embarrass him, Dudley turns the tables on the sneaky pair.
Arithmatically-challenged Beaver is mystified by a better than average grade on his report card, unaware that dastardly duo, Eddie Haskell and Lumpy Rutherford, altered the card en route to Ward's desk drawer.
Gilbert convinces Beaver that they should both make an ugly face when their class picture is taken. Beaver does it, but Gilbert doesn't. It doesn't get discovered until the picture has already gone to press to be in the school yearbook.
June is distressed when a series of trades with school friends nets Beaver a pet rat and when Ward tells Beaver to get rid of the rodent, Beaver sells the rat to Violet Rutherford. But, in spite of Violet's protests, Fred Rutherford demands that Beaver refund Violet's money and take the rat back, unaware that another member of the Rutherford family has also developed an affection for the furry little guy.
Wally's worries that little brother Beaver will disrupt the first teen party held at the Cleaver's house are realized when, on the way to the Whitney's house for a sleepover, Beaver takes a dare from Whitey to find out if there really is soup in a steaming billboard bowl.
Beaver and his friend Gilbert volunteer to collect Community Chest donations from the neighborhood so that June can attend a school open house with Wally. All goes well until the boys stop for ice cream and Beaver puts the money he collected into his back pocket...the one with the hole in it!
At first, mowing lawns seems like an easy way for Beaver and his friend Gilbert to earn extra money for summer, but no one seems to want their services and bad advice from Wally's friend Eddie results in an angry neighbor. When discouraged Gilbert opts to deliver newspapers instead, even after a nice lady offers to pay the boys $5.00, a determined Beaver decides to try once more; but what will he do when her check bounces?
When Beaver buys a wrecked 'coaster car' from Eddie Haskell, Wally pitches in to help his little brother fix it up and school chum Penny Woods promises him the wheels from her old doll buggy. But Beaver forgets his tools when he goes to Penny's house to remove the wheels and panics when he runs into his best friends, Gilbert and Richard, while trying to sneak the buggy home.
Wally takes his responsibility seriously when he is left in charge of the Cleaver household while Ward is in St. Louis on a business trip but isn't sure he can fill his father's shoes when Miss Landers sends Beaver home from school with a note for saying a bad word.