The International Baccalaureate's Middle Years Programme candidates will not receive grades for on-screen exams in core subjects.
The decision was posted by the IB on its website on 29 May, stating that pupils would not be awarded grades in cancelled e-assessments, which one headteacher branded a "stealth" announcement in that it was not communicated directly to schools.
In April, the board announced MYP exams would not go ahead, including on-screen assessments, but that an "MYP certificate will be awarded, reflecting achievements from a combination of personal project, e-portfolio subjects, and predicted grades from other subjects".
Subjects with on-screen assessments will now not have grades issued, and pupils wishing to receive a grade will need to take the exams in November 2020 or May 2021.
Background: What is the IB middle years programme?
Coronavirus: IB cancels Middle Years Programme exams
Coronavirus: International Baccalaureate cancels exams
In an update on the board's website on 29 May, the IB stated that the "May 2020 MYP on-screen examinations are cancelled, but with the option to take them in November 2020 (or May 2021)".
"For May 2020 this means grades will not be issued for subjects with on-screen exams," it added.
Subjects with on-screen exams include English, maths, humanities and sciences.
An international school head told Tes they felt this would severely disadvantage pupils over the long-term and prevent them from continuing on to further study.
The headteacher, whose school that runs the MYP programme, said the decision could leave pupils with "lifelong disadvantage" in comparison with those awarded GCSE grades.
They condemned "the stealth approach when announcing such a major decision - they [the IB] amended a paragraph on their Covid 19 response page and did not communicate this to schools, parents or students".
"I think that such decisions that leave MYP students at a lifelong disadvantage (imagine trying to apply for a 6th form college or university with no English, Maths or Science qualifications!) when compared to their GCSE counterparts need coverage and the educational world needs to be aware of this," they added.
An IB spokesperson said: “The IB is issuing grades for ePortfolio subjects and the personal project alongside the MYP certificate.
"IB assessed grades for the cancelled on-screen examinations will not be provided. Instead, in this exceptional year, the IB is providing a record of the predicted grades for the subjects that would have been assessed by on-screen examinations. Students may use all three documents provided by the IB for progressing onto their future steps.
"IB World Schools hold additional valuable information and data about their students throughout the MYP and will have their own individual processes in place for school based report cards and end of year reports.”