Mr Justice Calvert Smith dismissed the boy's case after hearing that, over a period of just six months, a 'vast catalogue' of up to 250 disciplinary incidents were recorded against him.
The youngster, named only as 'A' in court, was last year 'permanently excluded' from Old Swinford Hospital School, in Dudley, West Midlands, where he was a boarder.
The headmaster's decision was later upheld by the school governors and Dudley MBC's Independent Appeal Panel (IAP) - after a hearing lasting a marathon eight and a half hours.
However, the boy's counsel, Anne Lawrence - who presented more than 1,000 pages of documents to the judge in support of A's case - attacked the IAP's ruling that he had 'stolen' the phone as 'irrational' and his expulsion as 'disproportionate'.
She said the other pupil had 'lent' A the phone and, although he had 'misused' it, he could not have known the size of the bill he was building up.
She accepted A had had disciplinary problems in the past, but most incidents were 'minor' and he had never previously been accused of theft.
Expulsion was, in some cases, worse than a criminal conviction on a pupil's record, argued Miss Lawrence, who told the judge: 'A is still out of school. He can't get a school place.
'His mother has applied to over a dozen schools, but he can't get in. He has an appalling reference from his previous headmaster who clearly didn't like him.
'He is at home, having private tuition, when and if his mother can afford it'.
However, Mr Jonathan Auburn, for the IAP, told the judge that A's account was 'flatly contradicted' by the mobile phone's owner. A had, said the barrister, 'repeatedly lied' to school staff, insisting he did not have the phone until it was found in his bedroom.
Turning to A's 'appalling disciplinary record', Mr Auburn said he had previously been temporarily excluded three times from the school - once in 2004 and twice in 2005.
In the six months prior to his permanent exclusion, a 'vast catalogue' of 'approximately 250 behavioural and disciplinary matters' were recorded against him, added the barrister.
Mr Auburn said it was 'ridiculous' to describe expulsion as a 'disproportionate' penalty.
Dismissing the boy's judicial review challenge, the judge said he was 'quite satisfied' that a finding that A had - in layman's terms - 'stolen' the other boy's phone was open to the IAP.
Although he had 'borrowed' it initially, he had lied to the phone's owner and school staff about still having it and ran up call bills 'far in excess' of what one would normally expect between lenders and borrowers at a boarding school.
There was also 'voluminous' evidence of A's 'persistent misbehaviour' which 'clearly justified the action taken and could not conceivably be subject to judicial review'.
'In my view, there is no merit in this claim at all', the judge concluded, in refusing A's lawyers permission to take the case further, to the Court of Appeal.
Strand News Service