Lauriston Girls' School student Caitlin Louey was overjoyed when she opened the envelope containing her scores on Thursday morning - relieved her grades were likely high enough to secure her a place studying medicine at Monash.

Her friends Isabel Nakonieczny and Cassandra Murrell were also delighted at how they had fared and were glad the suspense was finally over.

"It was weird because everyone knew what they had scored, and we were still waiting a month later," Cassandra said. "I was like, 'what if I don't get what I predicted?'"

Isabel agreed: "People would always ask 'how did you go?', and we'd be like 'don't know'".

The International Baccalaureate is a globally recognised program that can open doors for students to study at overseas universities. It is offered at 14 schools in Victoria.

Students enrolled in the program are required to study a second language, at least one humanities or maths subject, a unit on the philosophy of knowledge, and spend a year working on a 4000-word essay on a topic of their choice.

They must also spend about four hours per week on creative efforts, sporting pursuits or community service over the two-year duration of the Baccalaureate.

Lauriston's IB coordinator Eirwen Stevenson said students liked the vigour, challenge and variety of the program. "We encourage them to take on something that's a little bit too hard - and manage it," she said.

On results day each student receives a score out of 45, and a perfect score converts to the highest attainable ATAR of 99.95.

At Presbyterian Ladies' College, three students - Jessica Tang, Elva Ren and Grace Ouyang - achieved a perfect result.

Grace said it had been "pretty surreal" opening the results envelope. "I couldn't believe it," she said. The result was far better than the 42 score she was expecting and should guarantee her a Chancellor's Scholarship at Melbourne University and a place studying Biomedicine.

The median score for PLC's 26 IB students was 38.6, with 92 per cent of the cohort achieving an equivalent ATAR score of 90 or above.

At Lauriston, 34 students opted to study IB and the median score was 38. Among the IB class, 85 per cent obtained an ATAR of 90 or more.

At Methodist Ladies' College, 96 per cent of the 50-strong IB cohort got an ATAR of 90 or above, and the median ATAR was 97.6. The school is also celebrating that two students got a perfect score of 45.

The median IB score for Tintern Grammar was 35. The school had 25 students undertake the IB Diploma in 2017 and 60 per cent achieved an ATAR of 90 or above.

At Tintern, the students received a call from the IB coordinator on Thursday morning telling them how they had fared, which student Eliza Mignot said made for a tense morning by the phone.

Eliza, who hopes to study an Arts/Science double degree at Monash, said she was drawn to IB because she feared her scores in performing arts and drama subjects would be marked down in the VCE scaling system. "I hated being marked down, even if I did well," she said. "The arts are not deemed to be incredibly academic, but you have to put a lot of work in and I hate the idea of being penalised."

The International Baccalaureate program is also offered at the Australian International Academy, Carey Baptist Grammar School, Geelong Grammar School, Ivanhoe Grammar School, Kardinia International College, Kilmore International School, Methodist Ladies College, St Leonard's College and Wesley College.

Albert Park College and Werribee Secondary College are the only two government schools to offer the program.