A total of £4,018,101.82 was spent on agency staff by schools in the borough between September last year and August this year.
For the start of the 2019/20 academic year, in September alone schools in the Dudley borough spent £205,982 on agency staff.
And 51 schools have paid to use agency staff between September last year and August this year, the figures released under a Freedom of Information request have revealed.
The figures include primary schools, secondary schools and nurseries. The overall figure also incorporated special schools and referral units.
The school which spent the most in the 12 months between September last year and August this year was Pens Meadow School, which spent more than £319,000.
Pens Meadow is a special school and offers places for 65 pupils aged between three to 16 years at a site in Stourbridge and Pensnett.
Special school Old Park, in Brierley Hill, spent the second highest sum – £277,633 – while Halesbury, in Feldon Lane, Halesowen, spent £251,206.
Queen Victoria Primary School, in Dudley, and Summerhill Secondary School, in Kingswinford, spent £194,409 and £167,825 respectively.
Schools in Dudley control their own budgets and decide when agency staff need to be brought in.
Other big spenders in the borough included St Mark's Primary School in Brierley Hill, which spent £143,051 in September 2018 to August 2019, and Dormston Secondary School in Sedgley, which spent £124,159 on agency staff.
Schools across Dudley spent £2.14m on agency staff in six months between September 2014 and February 2015, and figures covering the period from September 2013 to April 2014, showed that £2.8m was spent on agency staff.
Coseley Councillor Sue Ridney, who is Dudley Council's shadow cabinet member for children and young people, said schools bring in agency staff "reluctantly"
She said: "I am a chair of a school in my own ward and we set our budgets to try to cover so we don't have to use agency staff.
"Although we have employed part-time staff to cover part of the curriculum, obviously when staff are on maternity leave or long-term sick sometimes we do have to cover the absences with agency staff.
"That will be repeated in many schools.
"Some teachers find it hard with what goes in schools and some do go off on long-term sick and we need to cover that. Particularly with primary schools, teachers need to be in the classroom.
"Spending on agency staff is done reluctantly in schools. Children build up a rapport with their teachers and strangers coming in can be quite distressing and makes it difficult for them to learn.
"It is something we have to accept. It is important that children don't miss lessons due to teachers being off.
"The cost for agency staff comes out the budget and budgets can be quite tight – most run on fresh air."