That's according to research by the Australian Education Union, which on Wednesday revealed that this resourcing gap resulted in students missing more than $32 million per year in critical funding.

National figures state that 11.5 per cent of public school students have a disability. On that accepted figure, the AEU said they had compared this against the number of students currently funded for educational adjustments on the basis of disability.

The AEU said of the 62,255 students in the state, 4957 received this funding, leaving more than 2200 students falling through the gap.

AEU Tasmania president David Genford said the numbers were damning.

"We demand urgent action," he said.

"Even students with disability who are receiving funding are short-changed as state-federal agreements leave schools nine per cent short of the minimum funding required across the board."

"It's time to end the neglect of public education that has given us a teacher shortage and 2200 children without the support they require."

Tasmanian Disability Education Reform Lobby founder Kristen Desmond has been assisting the AEU. She said she respected this was a complex issue and that strides had been made to improve the situation through the Educational Adjustments funding model. However, the level of students being missed wasn't acceptable.

"The AEU's research confirms what we always suspected - that too many students with disability continue to miss out on appropriate support," she said.

"TDERL calls on the education minister to urgently review the way the Reasonable Adjustment model has been implemented to ensure students and teachers get support they need when they need it in the classroom."

Ms Desmond said a lot of the issue stemmed from the fact that the government doesn't know precisely how many students they have with a disability.

"If you ask the government today how many kids there are... they will tell you they don't know. I've been asking this question for the last 15 years.

"Fundamentally, you cannot tell me all students with a disability are getting adjustments and the resources they require when you can't tell me how many kids there are," she said.

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Ms Desmond said a key issue that needed to be addressed was the confusing communication eligibility for support.

"The new model doesn't matter if you are diagnosed or not. But I know from talking to parents that schools are saying they need a diagnosis. There's a long waitlist for allied health professionals, so kids are missing out for quite a substantial period.

The AEU has budgeted that the funding shortfall equates to $32.6 million per year, based off the secondary student disability funding loading amount - which is lower than that of primary funding loading.

Ms Desmond said the cost was even greater.

"At the end of the day, what it really costs is children's education."

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Education minister Sarah Courtney said the government was "committed to ensuring each Tasmanian student can thrive in an inclusive learning environment".

"We are supporting an additional 2000 students through the nation-leading Educational Adjustments needs-based funding model for students with disability, which is making a real difference in their lives," Ms Courtney said.

"Overall, it is estimated there is more than $90 million funding to support students with disability in 2021, and the Tasmanian Government is providing $56 million over four years in the 2021-22 budget to support the needs-based model, which has delivered an additional 51 full-time-equivalent support teachers."

She said an independent review of the model was planned for after 2022.

On allied health professionals, Ms Courtney said the government was focused on increasing access to speech and language pathologists, school psychologists and social works for Child and Family Centres.