Section 55B. A child who is before the juvenile court on a delinquency complaint or an indictment within the court's jurisdiction shall plead not delinquent, or that he should not be adjudged as a youthful offender, as the case may be. Such plea shall be submitted by the child and acted upon by the court; provided, however, that a child with whom the commonwealth cannot reach agreement for a recommended disposition shall be allowed to tender a plea together with a request for a specific disposition. Such request may include any disposition or dispositional terms within the court's jurisdiction, including, unless otherwise prohibited by law, a disposition request that a finding not be entered, but rather the case be continued without a finding to a specific date thereupon to be dismissed, such continuance conditioned upon compliance with specific terms and conditions or that the child be placed on probation pursuant to the provisions of section 57; provided, however, that a complaint alleging a child to be a delinquent child by reason of having violated the provisions of section 13B, 13B1/2, 13B3/4, section 22A, 22B, 22C or section 23, 23A, 23B or section 50 of chapter 265 shall not be placed on file or continued without a finding. If a plea, with an agreed upon recommendation or with a disposition request by the child, is tendered, the court shall inform the child that it will not impose a disposition that exceeds the terms of the agreed upon recommendation or the disposition request by the child, whichever is applicable, without giving the child the right to withdraw the plea.

Notwithstanding the foregoing requirements, if a child attempts to enter a plea or statement consisting of an admission of facts sufficient for a finding of delinquency or adjudication as a youthful offender, or some similar statement, such admission shall be deemed a tender of plea for purposes of the procedures set forth in this section.

Any pretrial motion filed in a delinquency case or case in which the commonwealth has proceeded by indictment pending in the juvenile court and decided before entry of the child's decision on waiver of the right to jury trial shall not be refiled or reheard thereafter, except in the discretion of the court as substantial justice requires. Any such pretrial motion not filed or filed but not decided prior to entry of the child's decision on waiver of the right to jury trial may be filed thereafter but not later than twenty-one days after entry of said decision on waiver of the right to jury trial, except for good cause shown.