To give a meaningful answer I think we need to know whether you are talking about the civil service exams in UK, India or indeed any other country as they will all be different
around 1845, the British started running public written examinations for those wishing to take on employment with the government.
This coincided with the beginning of pensions for civil servants.
Parodied as the Circumlocution Office in Dickens' Little Dorrit
So did I minty but chose to go into teaching instead (although I'm now in the Civil Service!). I'm actually not sure that entry method exists anymore. I'll try to find out.
Clerical assistant (later Admin) used to require 2 O levels including English, Clerical officer (later Admin) 5 O levels including English and Exec Officer 2 A levels. You could also get direct entry at EO with a degree which would usually put you on a 'fast stream' career path.
It's a bit more common now, Prudie for students to take 5 A levels. I don't understand why some students sit 14 or 15 GCSEs now though- we just did 8 ('O' levels as they were then)
1965 There was a boy at skool who 'taught himself' chemistry A level by reading the books
and was allowed to take it
I dont know what they did about the practical bit ....