Definition of junior schools:
(n) :
A school providing primary education to children.
(n) :
(Canada, chiefly Ontario) A school teaching children from kindergarten to Grade 5; an elementary school.
(n) :
(UK) A school providing education to children in Key Stage 2, i.e. for four academic years from September after a child's 7th birthday.
(n) :
(Australia) Usually a part of a private school that educates children between the ages of 2 and 5.