a schooly is someone that stays on at school in the sixth form, as they are choosing to stay at their school, because it is no longer compulsory for them to be there.
anyone in the sixth form that has stayed on at school.
people below sixth form are not schoolys.
The correct definition of a 'schooly', is a dump (shit) which is taken at school.
'Fuck that man, I ain't taking a schooly.'