Complaints to the Education Council about incompetent early childhood and primary school teachers have doubled in the past two years.
The number of reports about the two groups of teachers jumped from 56 in 2013 to 116 last year. A further 24 complaints were made about secondary school teachers.
The council and the Principals Federation said the increase was because principals and early childhood managers were more aware of the need to report problem teachers.
The council's manager teacher practice, Andrew Greig, said the complaints and mandatory reports by teachers' employers covered a wide range of problems.
"There's no one particular thing. It's to do with their knowledge and understanding of the curriculum, it's to do with their ability to understand where the students are at and what next steps need to be taken, and it's also to do with maintaining and establishing good relationships both with their students and with their fellow teachers."
Mr Greig said the council cancelled the registration of 23 of the 140 teachers reported to it last year, and found no problems with another 29.
The remaining 88 required further training and monitoring and by mid-February this year, four of those teachers had been deregistered while 12 required no further action.
Mr Greig said cancellation of registration was a last resort.
"If we decide that a teacher's not competent our main aim is to give them training to build them up to the required level of competence and so that's what we do first. It's only if they are so bad we feel we can't train them that we'll seek to cancel their registration."
He said the council had deregistered 27 teachers for incompetence in 2015, up from five in 2013.
But Mr Greig said the increase in the number of complaints and in the number of deregistrations did not mean there were more incompetent teachers, just that principals and early childhood teachers were more likely to report them.
Principals Federation president Iain Taylor said the increased number of complaints was due to greater awareness among principals that they should report teachers - and that was no bad thing.
"It's great that this is actually happening because in the old days a teacher would just leave and the principal would think 'great, they're out of my hair now' and don't have to worry about it, but now that mandatory reporting's there, we are reporting it to the Education Council and those teachers can't just get away with it."
Educational Institute president Louise Green said the number of teachers losing their registration each year was very low.
"We have not noticed any significant changes in the employment difficulties between teachers, principals and boards. In a big area such as education there are inevitable situations where this arises and we support the process that ensures professional standards are maintained."
The Education Council's figures showed no clear trend in the number of competence complaints about secondary school teachers, with 21 reported in 2013, 26 in 2014 and 24 last year.