Those who were not able to provide the data include some authorities who in 2018/19 had some of the highest rates per 1,000 pupils.
Ymhlith y rhai nad oeddent yn gallu darparu'r data mae rhai awdurdodau a oedd yn 2018/19 â rhai o'r cyfraddau uchaf fesul 1,000 o ddisgyblion.