The most common and most likely answer to this crossword clue is the 7 letter word CRAMMER
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More clues leading to the result CRAMMER
Buddy explains!

The straight part
We know that "school" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case school = crammer.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does CRAMMER mean?
CRAMMER noun- One who crams or stuffs.
- A book used for accelerated study in preparation for an examination.
- A student who studies hard for an examination.
- A teacher who aids such a student.
- A school whose speciality is helping students to pass certain examinations.
- (British slang) A liar.
- (British slang) A lie.