Mae asesu ac atebolrwydd yn hanfodol i godi safonau, ond mae gan y naill a’r llall rôl wahanol iawn i'w chwarae, mae asesu'n ymwneud â deall anghenion disgybl unigol ac mae atebolrwydd yn ymwneud â sut mae perfformiad cyffredinol yr ysgol yn cael ei werthuso. Ond mae'r gwahaniaeth rhwng y ddau wedi mynd yn aneglur, a hynny’n gallu cael effaith andwyol ar yr addysgu a’r dysgu.
Assessment and accountability are both critical to raising standards, but they each have a very different role to play, assessment is about understanding an individual pupil’s needs and accountability is about how the school’s overall performance is evaluated. But, the difference between the two has become blurred, which can have a detrimental effect on teaching and learning.