When class education is mixed (8)
I believe the answer is:
assorted
'is mixed' is the definition.
(I've seen this before)
'when class education' is the wordplay.
'when' becomes 'as'.
'class' becomes 'sort' ('sort' can be a synonym of 'class').
'education' becomes 'ed' (abbreviation - e.g. sex ed).
'as'+'sort'+'ed'='ASSORTED'
(Other definitions for assorted that I've seen before include "Containing various different kinds" , "Various, diverse" , "Odd-shaped" , "Mixed" , "Of different kinds put together, like sweets" .)