​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​C​hildren start secondary school in the September after their eleventh birthday.
​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ ​Mae plant yn dechrau yn yr ysgol uwchradd y mis Medi ar ôl eu pen-blwydd ​yn 11.