1.
a school for children between the ages of about 11 and 14 years, depending on the school's location.
2.
in the United Kingdom, a state-run school for children between the ages of about 8 and 13 years. The age range depends upon the local authority in which the school is situated.
3.
a school in the US for children between the ages of 11 and 14, after they leave elementary school