A Perth teenager has been jailed over a drag race which ended in a fatal crash.

The boy and his friend were racing through residential streets in Willetton in February 2011.

They were both 16 years old and learner drivers.

The court heard they reached speeds of more than 120 kms an hour before one of them crashed into another car, killing the 51-year-old driver.

He has already pleaded guilty to manslaughter, and served time in a juvenile facility.

The second teenager, who was not directly involved in the crash, was today sentenced in the Perth District Court to 14 months in jail, also on a charge of manslaughter.

He will be eligible for parole.