Police were called to a report of an injured child at St Joseph’s Primary School on Queen’s Road in Aberdeen at 9am on Tuesday.
Aberdeen City Council said the incident was caused by “a section of rendering material which became detached from a wall” at the school.
The boy has been taken to Aberdeen Royal Infirmary with non life threatening injuries.
A Police Scotland spokeswoman said: “The child’s family are aware and are with the child.
“Officers will be liaising with Aberdeen City Council and the Health and Safety Executive regarding the incident.”
A council spokesman said: “Our immediate priority is the wellbeing of the injured pupil and we are liaising with their family.
“The safety and wellbeing of all pupils, staff and visitors at Aberdeen’s schools is a priority for the council and a comprehensive response to this incident is ongoing.
“Whilst it would not be appropriate to comment further on the specifics of the incident at this early stage, we would seek to reassure the public that Aberdeen City Council is responding in line with established procedures.”