It depends a lot on the county and also "when" prior to 1968 in the county where I grew up you had grammar schools and secondary modern,(with pupils sitting an 11 plus exam) then they began to phase out the grammar schools. Then in the mid 70's to 1980's they went to a three tier system. infant school till the age 9, then "middle" junior school till 13, then comprehensive until 18. Then *sigh* back to a two teir system in the 1990's
I suggest you do a google search for the county council site of where you are setting the story, that should tell you whether they still have grammar schools or middle schools... It is a complex mess and can be a lottery as well, as to where your children go to school. I have known folk move house to get into the catchment area for a good school.