https://sites.google.com/hwbcymru.net/ysgol-y-dderwen/gwybodaeth-gyffredinol-general-information/presenoldebattendance
Ysgol y Dderwen - Presenoldeb/Attendance
www.sirgar.llyw.cymru/gwasanaethaur-cyngor/addysg-ac-ysgolion/colli-ysgol-colli-cyfle/
ysgolattendance