For two Sydney girls, scoring a perfect mark in their final year 12 exams also means they are the top students in the world.

Ravenswood student Ashley Masters, and St Paul's Grammar School student, Sarah Bakker, join a very select group of students around the world who achieved the highest possible result - 45 out of 45 - in their International Baccalaureate Diploma (IB) results, released in Australia on Thursday.

Redlands students Lori Zhou, 17, and Charlie Rogers, 18, both received 44 in the International Baccalaureate, or an equivalent ATAR of 99.85. Credit:Nick Moir

Ashley and Sarah's mark equates to an Australian Tertiary Admission Rank (ATAR) of 99.95 - the highest possible rank.

Sarah hopes to study law at Cambridge University and was in the United Kingdom last month for the highly competitive interviews, while Ashley is tossing up between medicine and medicinal chemistry at the University of NSW.