(1) Premature specialisation
A child's brain is designed to specialise at approximately the age of 16, you will find that the majority of students want to be able to choose the areas they study by this age. By delaying this you are forcing them to make some very tough decisions for university while allowing them to specialise early gives them the chance to decide what they like and are good at and what they don't like and are not so good at.
(2) no credit for extra-curricular
Because they recieve no official credit, then any extra curricular that they undertake can actually count for more in their CV and on their university applications. Universities are impressed by students that choose to undertake community activities etc.in their free time of their own choice rather then students who had no choice to.
(3) Driven by English political education imperatives
The A-levels are overseen and regulated by the British government therefore any decisions made by the government affect thousands of schools and are taken very seriously with only the students interests at heart.
(4) Distanced administration
In this day and age of "instant technonolgy" (e.g. email, fax, video conferencing etc.) why is distance a problem?
(5) Maladministration
The troubles encountered with Edexcel when the new A/S and A-levels were introduced in 2000 were in the main teething problems. Now that the boards have been amalgamated successfully they are up an running smoothly. Who is to say that what IB has to offer is error-free? In theory, a large new intake into the Diploma programme could upset the administration apple cart.
(6) Pressure of over assessment
The pressure of over-assessment in A-levels, in my opinion, is just the same, if not less than the IB. In A-levels a student can spread out their exams and retake any modules they were unhappy with. IB on the other hand forces them to take ALL their exams in two weeks and research indicates retakes are possible with the IB, but only the following May. Does this mean that parents are up for a third year of sixth form fees?. IB also has a significant amount of coursework compared with A-levels as well as a 4000 word "Theory of Knowledge" essay and a total of 150 hours compulsary community service!
(7) No coherent curriculum
A rather interesting phrase. The A-level curriculum is just as "coherent" as the IB. Does that mean there are millions of ex-students out there who have effectively wasted their sixth form because they didn't do IB! Do they have incoherent qualifications?
(8) Anglo-centric
At the end of the day parents send their children to A-level schools so that they can get an English education which is accepted worldwide, of course it will be Anglo-centric to some degree but this is clearly what the parents accept otherwise they would have placed their children elsewhere. The A-levels are not as Anglo-centric as made out, world history and literature is studied, RS focuses on worldwide religions, art on different cultures etc.