No longer kept a secret from pupils, put on pedestal outside? (12)

'no longer kept a secret' is the definition.
I can't tell whether this defines the answer.

'pupils put on pedestal outside?' is the wordplay.
'pupils' becomes 'class' (I've seen this before).
'put on pedestal' becomes 'deified' (I can't justify this - if you can you should believe this answer much more).
'outside?' is an insertion indicator (some letters go outside others).
'class' put within 'deified' is 'DECLASSIFIED'.

'from' is the link.

Can you help me to learn more?