The accident occurred around 7 am today when Raju, 14, and his sister Ishrat, 12, were going to school in Sarita Vihar near Shaheen Bagh.
"When Ishrat and Raju were walking near the footpath, the dumper lost balance due to a collision with the bus. It crushed Raju and Ishrat," Deputy Commissioner of Police Chinmoy Biswal said.
Ishrat and Raju were rushed to a hospital where she was declared brought dead while Raju is undergoing treatment, the officer said.
The two stayed in a slum and studied at a government school in Noor Nagar.