Teachers say schools are struggling in the South East as data shows the region is the worst hit by teacher shortages.
There were 276 vacancies in Kent, Sussex and Surrey last year, twice the previous year, government figures show.
The BBC understands one school was teaching multiple classes together in the school hall, a practice described as "educationally unethical".
The Department for Education said schools now have "more teachers than ever before".
DfE figures on staff recruitment show Kent is the local authority with the highest number of vacancies in the country. It had 135 unfilled positions last year - up from 44 in the previous year.
The number of teacher vacancies in England doubled from 1,100 in November 2020 to 2,300 in November 2022, when the latest DfE figures were released.
Mike Walters from the association of Kent headteachers said: "Teacher recruitment is as bad as it's ever been."
