Bottom Quartile Management

How can i posible identify the top midtop midbottom and bottom.
they will be dort from highest to lowest
then after that i would divide the lets say the headcount to 4 then distribute the top midtop midbottom and bottom
for example the headcount is 20, so 20/4 = 5, so the top midtop midbottom and bottom will be distributed bse on the sorting highest to lowest 
Also my Score is a measure because i wanted it to be dynamic 

for example this is the visualization i want 
personID | score
-----------|-------
A1 | 300   bottom
A2 | 320   bottom
A3 | 250   bottom
A4 | 310   midbottom 
A5 | 240  midbottom 
A6 | 250  midbottom 
A7 | 260  midtop 
A8 | 270  midtop 
A9 | 240  midtop 

A10 | 240  top 

A11 | 240  top 

A12 | 240  top 

Im really stuck with this problem. I badly need help. Thanks in advance