->''"The day I was born, I saved the world. Now I've helped to destroy it."''
-->-- '''Luke Smith'''

Luke and Maria start their first day at their new school, but not everything is as it seems, the cafeteria food is mouldy, the air smells like batteries, people are spontaneously getting ill and [[SincerityMode worst of all]], the portly head teacher has gas problems. Aided by their new friend, Clyde Langer, Sarah Jane and the gang discover a sinister revenge plot engineered by the Slitheen, for what the Doctor did to another branch of [[Recap/DoctorWhoS27E5WorldWarThree their family]].

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!!Tropes

* AdventureRebuff: Both Sarah Jane and Maria try to make Clyde go away for his own good. [[CaptainObvious It doesn't work]].
* AgeLift: Janine was supposed to be in her twenties in the script, but it seems the production was unable to find an overweight actress in that range, as in the broadcast version she is considerably older. The novelisation uses her originally intended age.
* BlandNameProduct: Clyde's Wolverine brand body spray, a play on the real brand "Lynx".
* ContinuityNod: Slitheen in Downing Street, which happened in "[[Recap/DoctorWhoS27E4AliensofLondon Aliens of London]]" and "[[Recap/DoctorWhoS27E5WorldWarThree World War Three]]", and Sarah Jane learned about in "[[Recap/DoctorWhoS28E3SchoolReunion School Reunion]]".
--->'''Sarah Jane:''' ''(remembering)'' Slitheen in Downing Street.
--->'''Maria:''' What?
--->'''Sarah Jane:''' Something a friend said once.
* DeathOfAChild: Implied but not shown; Korst, the young Slitheen, is wearing a twelve-year-old boy disguise that (given what is revealed about Slitheen disguises in their first ''Doctor Who'' appearance, and the real Mr Jeffrey is seen meeting a similar fate at the beginning of the story) must have been made by killing and skinning a real twelve-year-old boy.
* EvenEvilHasLovedOnes: The Slitheen beg Sarah Jane and the others to let the young Slitheen live.
* EvilTeacher: The Slitheen pose as teachers worldwide during their revenge plot.
* ExposedExtraterrestrials: Slitheen, when not in human suits.
* FatBastard: The Slitheen, as usual.
* {{Foreshadowing}}: The scene at the end when Clyde asks Mr. Smith where he came from and the computer responds by shocking him foreshadows a revelation in the season finale.
* TheGlassesComeOff: A rather dark version; when Blakeman is standing the real Jeffrey against the wall of the secret room so the Slitheen can KillAndReplace him, he pulls off Jeffrey's glasses as the Slitheen about to assume his identity won't need them.
* HoldYourHippogriffs: "Oh, for the love of Clom!"
* IncestSubtext: Between Glune, the headmaster Slitheen, and Kist, the science teacher Slitheen, which might help explain why [[IncestIsRelative the Slitheen are so screwed up]].
* KillAndReplace: All of the Slitheens' human disguises, although Jeffrey is the only one seen meeting this fate onscreen. (The novelisation adds a prologue where the real Janine is killed.)
* LargeHam: All of the Slitheen.
* LostInTransmission: As the Slitheen begin to drain London of power, Mr. Smith informs our heroes that the Slitheen are "notoriously hypersensitive to ''*fzzt*''", and they're left to figure out the end of the sentence from the information they already have.
* NiceJobBreakingItHero: Luke gives the Slitheen the equations they need in response to a transparent ploy that you'd have to have been born yesterday not to see through. Unfortunately for Luke, he ''[[YoungerThanTheyLook was]]'' born yesterday.
* TheNightThatNeverEnds: A variation -- instead of blotting out the sun, the Slitheen are trying to ''drain'' the sun of its energy.
* ParentalBonus: Maria's divorced mother asks her ex-husband if she can have the double bed size duvet as he won't need it having a single bed. Her mannerisms and delivery of this line is enough to make older viewers think she's making fun of his sex life.
* SchoolForScheming: The Slitheen have set up bases within schools worldwide to power their sun-draining machine.
* SecondEpisodeSubstitute: Clyde replaces Kelsey from the pilot as the snarky and obnoxious secondary companion.
* ShoutOut: "Let's have a ''Film/HighSchoolMusical'' moment. [[SarcasmMode A group hug will sort everything out]]."
* ToiletHumor: Luke doesn't understand it.
* TwoOfYourEarthMinutes: The teacher who's really a disguised Slitheen refers to "your... ''our'' main electrical supply".
* TheXOfY
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