A memorial to the victims was unveiled in the park in June, along with a separate commemorative mosaic at the school in nearby Wokingham, where Mr Furlong taught history.
Pupils said they wanted him to be remembered long after the last children he had taught had grown up.
The stone was designed in collaboration with the families of Mr Furlong, 36, Mr Ritchie-Bennett, 39, and Mr Wails, 49.
