A childcare worker accused of slapping two young children has been charged over a separate alleged assault of two girls.

Nepalese national Jayendra Jung Shahi, 24, is alleged to have struck four children while working at Panania Montessori Academy, in Sydney's southwest.

Police began investigating Shahi following reports two boys, aged three and four, were slapped on the face while trying to sleep on April 23.

Shahi was arrested over the initial allegations on April 26 but officers returned to his address, in Belmore, about 12.45pm on Monday.

Investigators alleged Shahi had also assaulted two girls, also aged three and four, in a separate incident.

He was taken to Campsie Police Station and charged with an additional two counts of common assault.

Prosecutors alleged the first incident was captured on CCTV.

'They are pretty serious examples of common assault, as they were committed in circumstances where the accused was meant to care for children in a childcare centre,' Acting Judge Amanda Coultas-Roberts said of the alleged assault.

'And whilst two of those children were sleeping, aged three and four, he slapped them across the face.'

Panania Montessori Academy, which opened last year, fired Shahi following his initial arrest. 

'We take any concerns of this nature extremely seriously, and the safety, health and wellbeing of children is always our highest priority,' the centre said in a statement.

'As soon as we became aware of the allegation, immediate action was taken including standing down the educator and reporting the matter to the police and regulatory authority.

'We have since terminated the educator's employment.'