To criticise, expose in print, show up, reprove. A scholastic term. Rebellious and idle boys are slated, that is, their names are set down on a slate to expose their offence, and some punishment is generally awarded.
“The journalists there lead each other a dance.
If one man slatesʹ another for what he has done,
It is pistols for two, and then coffin for one.”
Punch (The Pugnacious Penmen), 1885.