That is according to a Stormont Public Accounts Committee (PAC) report.
The cross-party committee also said “there are elements of dysfunctionality within the EA”.
The committee has recommended that the Department of Education (DE) hold an independent review of the EA to assess its effectiveness.
In February 2020, the EA apologised after a damning internal report found a number of failings in its SEN services.
The NI Audit Office (NIAO) subsequently questioned if the Education Authority’s procedures for pupils with SEN were “fit for purpose”.
The NIAO also found that the 26-week statutory limit for assessment and statementing of children was breached in the vast majority of cases.
The assembly’s PAC has also now released its report into Special Education Needs (SEN).
MLAs on the committee found “systemic problems” with provision for children with SEN.
They said that DE and the EA had spent £1.3bn on SEN in the past five years, with costs rising every year.
More than 67,000 school children have a reported SEN, while 19,200 with the most serious needs have a statement of SEN outlining the support they are to receive in school.
The PAC said that while the educational achievements of those children had risen, there were many failings in the way they were supported by the department and the authority.
“PAC remains concerned at the number of children that have been failed and how long these failings have been allowed to continue for,” their report said.
“In the committee’s view there are elements of dysfunctionality within the EA.
“PAC strongly believes that there is a need for an independent, external review of the effectiveness of SEN processes, to help build public confidence.”
The committee said there was an “absence of reliable information and data in the EA” which had led to poor performance by the EA.
MLAs said that failing needed to be “addressed urgently”.
‘Continually deliver a sub-standard service’
“The committee found that the number of children seeking to access SEN support is not known and as such there is a fundamental piece of work to be undertaken to establish the extent of unmet need,” they said.
“In the absence of this data, the EA cannot fully understand the demand for the services and identify the gaps in provision.”
The PAC acknowledged that the EA had begun to tackle the delays experienced by children waiting for assessments and statements.
“However, the committee remains deeply concerned and disappointed that children and their families had been failed for many years and the impact this has had,” the PAC report said.
The committee chair, DUP MLA William Humphrey, said that there was a culture within the EA “that has allowed it to continually deliver a sub-standard service for far too long”.
Mr Humphrey said front-line staff often gave “excellent” support to children with SEN, but there was a need for “an independent external review of the effectiveness of SEN processes” in Northern Ireland.