I cannot find any evidence to support Rawling's claim about the badge or even the motto.
Dorking High School was founded in 1884. It became Dorking Grammar School in 1931. The school's motto was Esto Fidelis as evidenced by this plaque:
http://ashcombedorkinian.com/htm/mem.../OldHeads1.htm
The plaque very helpfully has a companion which records that Dorking High School for Boys preceded it until it merged with the Girls High School in 1931. The school badge bears no resemblance to the one on the badge in any shape, form or symbology.
Helpfully, Dorking Museum has this plaque from Dorking High School which includes the school crest. It consists of the intertwined DHS letters which are of the same style as the post 1931 letters for Dorking Grammar School.
My eyesight is not sharp enough to read the motto but it does not appear to be the one on the badge in post one. It appears to me to be '..... et labore' Could be 'fide' or 'arte' which would translate as 'Skill and labour' or Faith and labour.'
Anyway Rawling's ID is definitely not proven by this and I believe it is incorrect. There are some other errors in his book such as the use of Bath Police Collar badges for Bath OTC which wore the Somerset light Infantry cap badge with permission from CO of the 1st Battalion SLI.
I have had a response from the school association. They did not have a cadet corps but an ATC was raised in WW2. The motto was not the one on the badge shown.
Rawlings appears to have been in error.