Mae bandio yn rhannu ysgolion, ar sail eu perfformiad, i un o bum band: o Fand 1, sef ysgolion sy'n perfformio'n dda, i Fand 5, sef ysgolion y mae angen i’w perfformiad wella.
Banding uses the performance of schools to group them into one of five bands – from Band 1, schools which are performing well, to Band 5, schools which need to improve.