Hill joined the IB in Geneva in 1993 as regional director for Africa, Europe and the Middle East, prior to which he was head of a bilingual IB Diploma school in France. He witnessed some of the criticism levelled against the IB during its formative years.

For example, the IB was at one stage associated with the Earth Charter (founded under the auspices of the UN), which encourages organisations and governments to focus on root causes of major problems and challenges facing humanity. This was perceived by some as introducing propaganda through the influence of an educational platform with the goal of engendering change in society.

The goal of the founding fathers of the first IB school, the International School of Geneva, some of whom were members of the League of Nations, was to replace the narrow-minded nationalist attitudes that had led to the outbreak of the first world war with "international mindedness".

However, critics accused the IB of promoting socialism, radical environmentalism and moral relativism, and suggested that its multicultural themes conflicted with traditional Judeo-Christian values and national sovereignty.

Now a visiting scholar at the University of Hong Kong's faculty of education, Hill says: "We have been accused of being un-American, Marxist and anti-Christian by certain groups. We don't believe we are any of those things. Profoundly not. While we do want students to be citizens of the earth, know about other cultures, be internationally-minded, and aware of global problems, we always say that if you know your own culture, you will have a reference point for appreciating other cultures, and that is terribly important to us."

"We have certain things we do believe in, such as being conscious of the environment to preserve the planet for the future, but we are not fanatical about it. We are aware of human rights and respect for people, and that starts at home, then goes local in a small way, and then goes international."

"People choose to interpret and read what they wish, and that is OK, because that is what the IB is about. The IB teaches students to analyse critically why people are saying this. What is their background? They are entitled to their opinion, and we would simply leave it up to parents and students to make up their own minds about detractors of the IB," he says.

Parents have certainly made up their mind about an IB education, as Hill predicts the IB will have 10,000 schools and 2.5 million students, and will be offered in 20 languages, by 2020. He predicts PYP will be the largest of the programmes, and that all DP students will probably take some courses online.

So how does this vision of continued growth affect the quality of teaching procedures, practices, and assessment?

As a long-standing IB educator, I have personally known of instances of inconsistencies in the marking of the internal assessment component of biology. Can these be attributed to the challenges of adhering to criteria across a growing body of examiners, and the growing need to monitor cohesiveness and the ability of technology to keep up with this vision?

"No examination system is perfect - and the IB is not a perfect system either," Hill says. He adds that that the IB is complex, as it works across the world, and across different cultures. But he believes such instances to be few, and when the IB becomes aware of them, it is quick to address them. "While there are glitches, students have not been disadvantaged," he asserts with conviction.

He draws attention to studies undertaken independently by researchers that find IB assessment to have been stable over the years. Assessment in some educational systems has made it difficult for universities to differentiate between good students, and particularly between those at the top. This has required universities to adjust their admission criteria for several secondary school qualifications.

"I believe IB grades are well accepted by universities, who know that if a student gets six out of seven in HL biology then it does not matter if he or she comes from the International School in Geneva, or from one outside Accra, in Ghana, which has as many orphans as students.

"I like this aspect of the IB, because it's all a matter of what the student achieves in relation to the assessment criteria, which are the same worldwide. This also provides equal opportunity for university entrance, no matter where you come from," he says.

Several procedures, including a curriculum review cycle for each subject, ensure this will continue. The highly centralised IB examination centre, located in Cardiff, Wales, has one chief examiner per subject overseeing a final committee that makes decisions regarding grades awarded to all students after cross-marking across subjects and instructional languages.

Subject papers are now marked online via a "seeding" process which has brought about improvement in accuracy among the increasing number of examiners. A seed is a marked paper that is introduced during online marking and assesses the examiners adherence to the marking criteria.

"Even in Theory of Knowledge and literary essays, which are regarded as more subjective to mark, there is a more standardised procedure with seeding. [It is possible] to indicate criteria regarding answers that are being sought while leaving enough room for the student to be creative," says Hill.

But what about the notion that an IB education is for the elite? "Nearly 57 per cent of IB schools are state government schools where students don't pay fees, and this proportion is increasing gradually around the world. That is a very good thing, as it lets in students who would normally not have gained access," says Hill.

"Although we have a lot of expat schools in the developing world that can look after themselves financially, we would like to see more national schools in Africa and Latin America, and a few more in Asia."

The access and advancement committee under the Geneva-based IB Organisation looks at different ways of providing students access to an IB education. That includes a grant of up to US$10,000 dollars per school, and Open World schools where students from a non-IB school can undertake the DP through an IB mentor or "parent" school.

Some of the lessons could be online, and some by distance teaching, while students attend their own school.

The IB pedagogy aims to strike a balance between subject depth and breadth, didactic and constructivist philosophies of teaching, subjects that are interdisciplinary while maintaining the integrity of their own disciplines, and ensuring that learning occurs via cognitive and affective domains.

Hill says: "Academic rigour is important, but the IB's humanitarian values are everything."