Section 57. Every case of a delinquent child shall be investigated by the probation officer, who shall make a report regarding the character of such child, his school record, home surroundings and the previous complaints against him, if any. In every case involving a child attending a special class authorized by law, he shall secure from the bureau of special education a record of performance of said child. He shall be present in court at the trial of the case, and furnish the court with such information and assistance as shall be required. At the end of the probation period of a child who has been placed on probation, the officer in whose care he has been shall make a report as to his conduct during such period.