Police are seeking information about shattered Hillsbus windows.
The inquiry relates to two separate incidents in The Hills, captured on video.
Police said a Hillsbus was travelling west on Glenhaven Road, Glenhaven, about 4.35pm September 3 when it stopped to pick up a school girl.
As a ute passed, a side window of the bus shattered, near where the girl was, a police spokesman said.
He said another Hillsbus stopped in Annangrove Road, Kenthurst, about 3.49pm to pick up school students.
In the video footage, it appears as if the same ute — a dark blue, four-door Holden Crewman — passed this bus.
A rear window shattered as the students got on.
Police said the vehicle, which appears to have had three occupants, was towing a dual axle trailer fitted with a drop-down rear gate that also acts as a ramp.
The trailer was carrying a ride-on mower and other gardening equipment.
■ Anyone with information should call Crime Stoppers on 1800 333 000.