I am currently studying for the Grade 6 violin exam and my teacher has suggested two pieces for the exam that are listed on the official syllabus (out of the six for each section) but are not included in the three within the official ABRSM score book.

Can anyone tell me how I can obtain the score that ABRSM prefer?

Many thanks,

The syllabus does give the recommended publisher , so ask you teacher or check from the syllabus on this website (Click on exams at the top)

They are not 'preferred' scores, they are merely suggestions. You can use whichever edition you like, unless it specifically says 'this edition only'.

(An old teacher, a Senior Examiner for ABRSM told me this)

As others have said, you won't be in any way penalised or disadvantaged for using an edition that isn't the one listed.

With pieces such as the Seitz or Mollenhauer, it makes sense to go with the suggestion, because those volumes will provide you with plenty of other repertoire to work at besides exam pieces. For Vivaldi or Handel, getting a good-quality modern edition such as those published by Henle Verlag or Barenreiter would be my recommendation.