The International Baccalaureate has been accused of failing to ask schools whether running exams this year would be fair to students who have faced huge disruption to their education.
Last week, the IB launched a schools survey asking whether they felt they could run the May series safely following the government's cancellation of GCSEs and A levels this year.
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But Mark Sully, the deputy headteacher at Warminster School in Wiltshire, said that the consultation had "failed to ask the most important question" about whether it would be fair to students whose disruption has been disrupted by the pandemic.
Writing on social media, he said: "Your two questions focused on whether the school could administer the exams in May and you failed to think about the students who are having to sit the exams.
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"Surely the students are the most important consideration as to whether exams can be taken or not? The poor students, worldwide, have had such a difficult time during their IB course, and in our school's case the students will have missed 40 per cent of their live teaching during the two-year programme, not to mention all of them having to self-isolate for two weeks due to a positive Covid case, as well as those who have had to quarantine upon departure or arrival to school," he added.
Mr Sully said students would not be in a position to "fairly sit the exams in May", given the varied levels of disruption caused to IB students by the global pandemic.
... position to fairly sit the exams in May with every IB student worldwide having experienced varying levels of interruption to their learning. I implore you to put the students first and think of their mental health and needs. @tes @CathImogenLough @ofqual @educationgovuk— Mark Sully (@marksully9) January 13, 2021
Other school leaders have expressed concern over the approach taken by the IB.
Rod Jackson, head of ICS London International School, a 3-18 independent school in London, said he felt the survey was a "blunt instrument" to assess whether students could take exams.
"We completed the IB questionnaire this morning and I felt it to be quite a blunt instrument with the emphasis... in the wrong place," he told Tes.
Mr Jackson said he felt the focus was "on the school logistics rather than the students’ readiness".
"The former issue has already been answered by the UK government which has decided that external exams (GCSEs and A levels) should not take place - there is no reason why IB exams should be any different," he added.
"Covid has impacted the learning of this cohort of students far more than the May 2020 cohort.
"The IB has said they will make a decision in February, which is late for schools and students.
"We need to know whether the exams will take place and if not the process that will be used to calculate grades."
Last year Mr Sully wrote to the Department for Education after IB students and teachers expressed their anger when many had received lower grades than they had expected.
He told Tes that the IB survey this year asked schools whether they were teaching completely face-to-face, completely online or a mixture of both, and whether they could safely administer exams in May - where IB coordinators could answer "yes" or "no" with an open box for comments.
"I wouldn't suggest this is much of a consultation and is definitely not asking for our opinion on whether the students will be in a fit state to access the exams," he said.
The IB has been contacted with a request for comment.