In the UK, at least, we use the term "a schoolboy error" to mean a simple or foolish mistake.
Oxford has it as:
British informal
A very basic or foolish mistake.
It is used very frequently in sports, especially football (soccer) which I watch a lot. Schoolboys are very much amateur and can be expected to make simple errors and I wonder if it was in football that this phrase originated.
Away from sport, I have seen the term used in politics, entertainment, finance, and news. Everywhere really.
What I can't find, however, is the phrase's first usage. If first used in an academic sense, how did the term transition into its current mainstream usage?
Anyone care to help?
Best Answer
Dan Bron is certainly correct (in his comments above) in pointing out that "schoolboy error" is associated in the first instance with errors typical of the ones that schoolboys make in class. Searches of Google Books yield seven matches for "schoolboy error[s]" between 1846 and 1867. All of them have the same general sense, and all are from British periodicals. The earliest is from a review of The Step-mother by G.P.R. James, in The Athenæum (April 11, 1846):
From "Barnes' Notes on the New Testament," in The Bible Review (October 1847):
From "Construction of Artillery," in The Civil Engineer and Architect's Journal (January 1857):
From H.D. Garrison, "A Reviewer Reviewed," in The Eclectic Medical Journal (December 1858):
From "Books of the Quarter Suitable for Reading-Societies," in The National Review (April 1861):
From "To Dishley Peters, Esq." in The Musical World (February 10, 1866):
From a review of Henry Maudsley, "The Physiology and Pathology of the Mind," in The Saturday Review (May 25, 1867):
It follows that a "schoolboy error" was originally conceived of as the sort of mistake in writing, reasoning, or declaiming that a schoolboy was liable to make.