Secondary schools fear they could lose thousands of students to polytechnics and other tertiary institutions next year.
Thursday's Budget trebled the number of Youth Guarantee places from 2500 this year to 7500 next year.
The Government is shifting funding from training programmes that prepare 16- and 17-year-olds for jobs to programmes preparing them for further training and education.
It is not clear how many more students will leave secondary school because of the change, but Secondary Principals Association president Patrick Walsh is sounding warning bells.
Mr Walsh says schools and polytechnics could end up competing for students.
Post Primary Teachers Association president Robin Duff agrees the increase could cost jobs at schools, but supports the aim of keeping young people in education and training.
However, the chief executive of the Eastern Institute of Technology, Chris Collins, says the groups need to work together and schools will benefit if struggling students take up Youth Guarantee places.