Finds fault with outdated school equipment (6)
I believe the answer is:
slates
'finds' is the definition.
The definition and answer can be both related to thinking as well as being verbs in their -s form.
Maybe you can see a link between them that I can't see?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for slates that I've seen before include "Thin layers of rock for roofing" , "Strongly criticises the roof tiles" , "Strongly criticise the roof tiles" , "Abuses with roof tiles?" , "Criticises severely using roof coverings" .)