The car smashed into barriers in Langworth, Lincolnshire, on Thursday after failing to stop for police.
The car's driver was airlifted to hospital, with what police described as serious injuries.
An 18-year-old man, and two women, aged 18 and 19, said to be passengers in the car, were arrested.
Lincolnshire Police said a 16-year-old boy remains in a serious condition at Queens Medical Centre in Nottingham, and a 15 year-old boy is receiving treatment at Lincoln County Hospital.
The force said the incident has been referred to the Independent Police Complaints Commission (IPCC) due to the police's involvement.
Three teenagers from South Yorkshire have been arrested after a "suspected stolen car" crashed into a railway level crossing.