Po-faced about school sending colourful types in a number of directions (5)
I believe the answer is:
prism
'sending colourful types in a number of directions' is the definition.
I can't judge whether this definition defines the answer.
'po-faced about school' is the wordplay.
'po-faced' becomes 'prim' (I am not sure about this - if you are sure you should believe this answer much more).
'about' indicates putting letters inside.
'school' becomes 's'.
'prim' placed around 's' is 'PRISM'.
Can you help me to learn more?
(Other definitions for prism that I've seen before include "Triangular shape of glass or quartz, breaks up a beam" , "Light transmitter" , "Light-bending glass" , "Glass triangle, separates light into colours" , "Shape used to disperse light beams" .)