Head teachers in England are having to share staff with other schools as they try to find “stop-gap solutions” to fill vacancies, the Association of School and College Leaders says.
Its snapshot survey of 900 heads found 90% were struggling to recruit.
The government says it is investing £1.3bn up to 2020 to attract new teachers where they are most needed.
But three-quarters of respondents to the survey said it was now tougher to recruit than 12 months ago.
And nearly nine out of 10 said the situation was creating extra work and stress for staff.
While some 70% were using more support staff, about a fifth had worked with other schools to share or recruit teachers.
Some 41% of those surveyed had arranged for more lessons to be taught by the head or deputy head.