Roedd lleihau maint dosbarthiadau babanod yn rhan allweddol o’r Cytundeb Blaengar rhwng Kirsty Williams a Phrif Weinidog Cymru. Yn unol â thystiolaeth ryngwladol, mae’r polisi’n targedu’r ysgolion a fyddai’n elwa fwyaf ar gael dosbarthiadau llai, fel ysgolion â lefelau uchel o amddifadedd, anghenion dysgu ychwanegol a/neu lle mae angen gwella'r addysgu a'r dysgu.
Reducing infant class sizes was a key part of the Progressive Agreement reached between Kirsty Williams and the First Minister. In line with international evidence, the policy targets schools that would most benefit from smaller classes, such as those with high levels of deprivation, additional learning needs, and/or where teaching and learning needs to improve.