A judge has backed magistrates who gave a 12-year-old Essex boy a custodial sentence for committing more than 30 crimes in less than 18 months.
The youngster became one of the UK's youngest inmates when Witham Magistrates' Court sent him to a detention centre for 10 months.
Judge Laura Harris rejected his appeal at Chelmsford Crown Court.
Magistrates had been told the boy, who lives near Chelmsford, had convictions for assault and vehicle theft.
Prosecutors said the boy, who cannot be named because of his age, had breached "many" previous court orders and committed "many" offences while on bail.
Magistrates ordered him to be detained after he had admitted assaults on a woman and a man and taking a car without consent then driving dangerously.
They said he would be eligible for release after serving at least five months in a detention centre.
The boy's lawyers argued that sentence was "manifestly excessive".
But Judge Harris said the youngster's offences were serious and all attempts to "work with him" had failed.