Without all of the facts, it's impossible to know what might happen in this case.
It's usually pretty difficult to charge a 15 year old in adult court, unless the crime is murder or certain sex offenses, the minor personally used a firearm, the crime was committed for a criminal street gang, or a number of different factors listed in Welfare & Institutions Code 707(b). Right now, I don't see any of those present... but, of course, you've only posted some basic facts.
A conviction for residential burglary in adult court carries a prison term of 2, 4 or six years in prison. It is considered a "strike" under the Three Strikes law and can be used to increase the punishment for any future felony. It is also "prison presumptive," which means a person convicted of this offense MUST be sentenced to prison unless the judge makes a finding that the circumstances justify probation... for instance, if the defendant is young or elderly, and has no prior record. Finally, since someone other than an accomplice was in the home at the time, it is considered a violent felony and a person convicted of this offense would have to serve 85% of the prison sentence (instead of half) before being released on parole.
If the case stays in juvenile court, the judge is supposed to focus on rehabilitation, not punishment. The minor could be placed on probation, sent to a group home, or even to the Juvenile Division of the state prison system (formerly known as the California Youth Authority).
Please understand that this is a general discussion of legal principles by a California lawyer and does not create an attorney/client relationship. It's impossible to give detailed, accurate advice based on a few sentences on a website (and you shouldn't provide too much specific information about your legal matter on a public forum like this site, anyway). You should always seek advice from an attorney licensed in your jurisdiction who can give you an informed opinion after reviewing all of the relevant information.
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