Parents and teachers are being drafted in to oversee GCSE and A-Level exams due to a shortage of trained invigilators.
Unions warned that exam monitors were being put off by fears of catching Covid in schools, leaving heads scrambling to plug the gaps.
Schools are diverting staff from other work to oversee tests as GCSE and A-Level exams began this week.
Some schools have even appealed to parents to step in, according to the Association of School and College Leaders (ASCL).
A recent survey by the union found more than a third of schools had not been able to recruit enough invigilators for this summer's exams.
ASCL General Secretary Geoff Barton said: “Some of our survey responses indicated that some schools have put out appeals to parents to come forward as one way of filling a shortfall in invigilators. "
Shortages of trained invigilators could cause more disruption for schools, he warned, which are already trying to catch up after the pandemic.
Mr Barton said: "The shortages appear to be mainly caused by a combination of individuals being less inclined to work as invigilators because of worry over the Covid situation and an increase in the number of students making requests to sit their exams in separate rooms away from the main exam hall because of high levels of stress and anxiety.
"Many people who work as invigilators are retired teachers, may be concerned about the risks of catching Covid, and therefore not keen on the idea of being in an exam hall with a large number of students particularly as the government has withdrawn free Covid testing.
"We have repeatedly called upon the Government to make free Covid tests available to students sitting exams which may have helped to allay these concerns, but the Government has refused to do so.
"We do not think this is consistent with its rhetoric about the importance of exams."
Mr Barton warned that redeploying staff from other duties "is likely to have an impact on provision".
Sarah Hannafin, senior policy adviser for the NAHT school leaders' union, said schools were facing challenges preparing pupils for formal exams after Covid disruption.
She said: "Our members have reported an increased demand for access arrangements including requests for separate or small room invigilation and many of these are linked to increased student anxiety which also create additional challenges for more invigilators and spaces to use."
She added: "Most of these students have not taken external exams before and nor have they seen their peers take them over the past two years, so there is a real need to make sure they are familiar with the processes and rules, confident in what to expect and can therefore focus on doing their best in the exams."
Jugjit Chima, chief executive of the National Association of Exams Officers, said that some schools had been late to recruit invigilators because they had not been convinced that exams would go ahead this year following Covid cancellations.
"We've almost had a perfect storm this year," he said.
One invigilator must be present in written exams for every 30 students usually but this requirement has been relaxed to one for 40 students because of the shortages.
A DfE spokesperson said: “We do not anticipate general disruption as a result of a lack of invigilators.
"Schools and exam centres are well prepared to handle any challenges, having been asked to have robust contingency plans in place.
“We know some schools and colleges have had difficulties recruiting invigilators this year, which is why we have been working closely with exam boards and with the Exams Office, who developed a Vacancy Map that collates centre invigilator vacancies in one place, and which we have shared widely in the run-up to exams.
"Exam boards have also introduced additional flexibilities to the rules surrounding invigilation – should they be needed.”
