Even staff often see them as a bit of a laugh.
But one school worker didn't see the funny side when she slipped on steps smeared in Vaseline by de-mob happy sixth-formers.
Linda Gillie, 53, needed hospital treatment for head and leg injuries as a result of the end-of-year "joke" at Galashiels Academy in the Borders.
Now the assistant janitor is suing Scottish Borders Council for £50,000.
Her lawyers argue council staff did too little to clampdown on practical jokes by pupils at the school, which they claim has a long history of the problem.
Papers lodged at the Court of Session in Edinburgh state Mrs Gillie was asked by a teacher on May 12, 2009, to clean up Vaseline which had been smeared on the bannister of a staircase near the school's science department.
The papers add: "The Vaseline had been placed there by sixth-year pupils as a prank. In addition, there were condoms placed on door handles.
"Unbeknown to Mrs Gillie there was also Vaseline on the steps. She slipped on the Vaseline, falling downstairs suffering loss, injury and damage."
After the accident she was taken to hospital, where she was diagnosed with a mild head injury and generalised limb bruising, her lawyers say.
She later had procedures under general anaesthetic to remove a fluid swelling in her left leg. She was left with a 5in scar and unable to return to her job until October 2010.
Her lawyers claimed sixth-year pupils at Galashiels Academy habitually carried out pranks in their last week. They pointed to incidents where pupils threw eggs and tomato ketchup at the school, placed sardines in lockers, left dirty nappies in the school, left fish in the library, put washing up liquid down the toilets and black boot polish on seats.
In another case, it is alleged an English teacher was sprayed with sardines hidden in a hand-drier.
Mrs Gillie is blaming the education authority for not doing more to halt the pranks.
Her lawyers say Galashiels Academy did not introduce a hall monitor and claim other schools in the area discouraged sixth-year pupils from attending in the last week to avoid pranks.
The papers allege: "On the date of [Mrs Gillie's] accident, many sixth-year pupils had arrived at school without their uniform, were in Bermuda shorts and in buoyant mood."
The authorities, they claim, were "accepting of the lack of uniform and took no steps to avoid pranks being performed".
They go on to say that, since the accident, pranks were discouraged. Instead, the school "arranged barbecues and water fights in the last week to provide an outlet for the school-leavers' inclination to play pranks".
But lawyers for the council claim in papers lodged at the court: "The circumstances of any incident on May 12, 2009, are not known and not admitted."
A spokesman for the council said: "I can confirm this claim has been litigated. It would be inappropriate for us to comment any further."
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