what did the judge want to do with boo ?

The judge wanted to send Boo to the state industrial school like the other boys with whom he got into trouble. Boo's father thought that was a disgrace and convinced the judge to release Boo into his custody.

When Boo was a young man and had been causing trouble, he had come before the court. He faced being put in a home for delinquents but his family fought the ruling to have him at home under strict curfew conditions. From this time, Arthur 'Boo' Radley was not known to leave the house, and his brother apparently carried on the incarceration after their father had died.