Section 24P. (a) Upon evidence that a person under the age of 21, after having been arrested for or charged with a violation under section 24, 24G or 24L, had a blood alcohol percentage of two one-hundredths or greater or upon evidence that such person refused to submit to a chemical test or analysis of his breath or blood under section 24, notwithstanding the finding upon any such charge, such person shall have his license or permit to operate a motor vehicle suspended by the registrar for a period of 180 days; provided, however, that any such person who is less than 18 years of age at the time of such violation shall have his license suspended by the registrar for one year. Such suspension by the registrar shall be imposed in addition to any penalty, license suspension or revocation imposed upon such person by the court as required by said section 24, 24G or 24L.

If a person has not been previously arrested for or charged with a violation under said section 24, 24G or 24L, such person shall, if he consents, be assigned to a program specifically designed by the department of public health for the treatment of underage drinking drivers; provided, however, that such assignment shall not be precluded by a finding or disposition upon a charge against such person under said section 24, 24G or 24L. Upon entry into such program, as authorized by this section or as otherwise required under any disposition pursuant to section 24D, the suspension of a license or permit to operate as required by this section shall be waived by the registrar for a person under 21 years of age but over 18 years of age; provided, however, that such suspension shall be for a period of 180 days for such person who was under the age of 18 at the time of such violation. Upon the failure of a person under the age of 21 to successfully complete such program, the registrar shall forthwith suspend such license or permit to operate for 180 days; provided, however, that upon such failure to successfully complete such program by a person who was under the age of 18 at the time of such violation, the registrar shall forthwith suspend the license or permit to operate for one year.

(b) The license or permit to operate of a person convicted of any violation under section 24, 24G, 24I or 24L who was under the age of 18 at the time of such violation and whose license or permit to operate was not suspended under subsection (a) for such violation shall have such license or permit suspended for a period of 180 days for a first offense and for a period of one year for a second or subsequent offense.