Substitute cover by prematurely-retired teachers cost the Northern Ireland taxpayer an extra £6 million, it has been revealed.
During 2008/9, 33 people who stepped down early were re-employed to provide temporary teaching. Most were well-paid former principals and vice-principals, a Stormont report said.
Massive savings could have been made if newly-qualified teachers had provided cover for sick or absent staff instead, a review by the Public Accounts Committee (PAC) added.
The report said: "The fact that so many of our newly-qualified teachers are unemployed or under-employed is a tragedy not only for the individual teachers but also for the school system here and our pupils.
"In the committee's view, there is an obligation on the part of the department (of Education) to provide a fair and appropriate level of opportunity for these new teachers."
Long-term sickness was responsible for £1 million of the spend in 2008/9.
The committee acknowledged that the department has put a range of procedures in place to try to curb the use of prematurely-retired teachers as substitutes and improve the opportunities for their younger counterparts.
"In the committee's view, however, it is time for the department to bear down much more heavily on this problem and rethink the fundamental assumptions behind the current system and make some far-reaching changes to the way substitution cover is managed," it added.
The department acknowledged that, as it has responsibility for developing the regulations on the re-employment of prematurely retired teachers, it is within its powers to end the practice.
The report warned: "The committee is disappointed that the department did not show the will, following the previous report, to amend the premature retirement regulations to ensure that any teachers who had benefited from enhanced settlements, in particular, were barred from subsequent re-employment as a substitute teacher."