The figure was revealed by the SDLP MLA John Dallat at a hearing of the Public Accounts Committee (PAC).
It followed an assembly question.
Mr Dallat, the vice-chair of the committee, also found that of the 106 teachers suspended over the same period, six had eventually been dismissed.
The figure of £4.2m does not include any costs of paying for substitute teachers to cover the suspended teachers.
In 2014/15, £1,272,440 was paid out, a rise from £974,992 in 2013/14.
Mr Dallat told the committee that something must be "badly wrong".
"Either you can't sack teachers, or teachers are being suspended when they shouldn't be," he said.
In response, a Department of Education (DE) official said that the overwhelming majority of the teachers had been reinstated.
Paul Sweeney said DE was working with the employing authorities to see if suspensions could be resolved more quickly.
"One couldn't be content with those sums of money being deployed in that manner," he told the committee.
The exchange took place during a PAC hearing into a recent Audit Office (NIAO) report on school sustainability and the number of empty places in schools.
The report found that the number of empty places in schools in Northern Ireland was around 71,000, about one fifth of the entire number of places available.
A number of members of the PAC questioned DE officials on what they were doing to reduce the number of surplus places.
UUP MLA Roy Beggs said the department was relying on "inaccurate figures" when it came to calculating the number of empty places, while Trevor Clarke of the DUP said that DE was relying on an "old methodology" which was "outdated".
Mr Sweeney said that calculating school capacity was not an "exact science" and it was "complex" to come to a definite figure for surplus places.
Sinn Féin MLA Phil Flanagan also raised concerns about how a school's maximum enrolment was calculated.
"I can't understand how officials within the department or the managing authorities never identified this as a problem, particularly when you were engaging in such an extensive process as the area planning process," he said.
Questioned further by Mr Flanagan on the process, Mr Sweeney said there was no "hidden hit list schools that we are going to close".
More than £4m has been spent on wages, national insurance and pension contributions for suspended teachers over the last five years.