(1) An appeal under section 337 must not be conducted as a rehearing.
(2) On an appeal under section 337, if the appellate court considers that the respondent has failed, wholly or partly, to fulfil the undertaking referred to in section 337(1)(a), the appellate court may—
(a) set aside the sentence imposed by the Children's Court; and
(b) impose the sentence that it considers appropriate, having regard to the failure of the respondent to fulfil the undertaking.