Mae’r newidiadau i gymwysterau a mesurau perfformiad yn golygu nad yw’n briodol cymharu canlyniadau TGAU eleni a’r llynedd na chwaith bod y cymariaethau’n gywir, rhybuddiodd yr Ysgrifennydd Addysg.
Changes to qualifications and performance measures mean that comparisons between this year and last year’s GCSE results are not appropriate or  accurate, the Education Secretary has warned.