Job losses in schools caused by falling pupil numbers are being balanced by increased demand for staffing to implement the workload agreement, according to a TES Cymru survey.
Local education authorities say the rolling-out of the foundation phase in primary schools is also expected to boost school staffs.
A TES Cymru survey of 13 of the 22 Welsh LEAs reveals 116 teacher and non-teacher job losses in schools, including a handful of redundancies and non-renewal of temporary contracts. Another 123 (almost all teachers) are taking early retirement. At least 49 of these would otherwise be redundancies, say LEAs.
But headteachers fear an "alarming" number of job losses are not appearing in official redundancy figures because they involve short-term contracts which have not been renewed.
Anna Brychan, director of the National Association of Head Teachers Cymru, said: "We may not yet appreciate fully just how many jobs are disappearing across the school sector."
Only a few LEAs were able to comment on the loss of posts through non-renewal of temporary or short-term contracts, but in just four of them, 40 such teaching posts were expected to go. Several LEAs were unable or unwilling to supply figures because job losses are still being negotiated with schools.
Overall, however, most LEAs are expecting the number of teachers to remain roughly the same as last year. Eight said support staff numbers would be up or stay the same, although none expected teaching numbers to rise.
Half of those sampled blamed falling pupil numbers for staff changes, including Swansea, which registered the highest number of job losses - 63, including 36 early teacher retirements.
A spokesperson also blamed rising energy costs, efficiency cuts due to the Gershon review of the civil service, schools maintenance costs and the reduction of grants.
In Powys, LEA staff are predicting a stable teaching force but around 35 more support staff.
A spokesperson said: "Staffing levels are expected to increase in 20067 because of the introduction of the foundation phase and the 14-19 agenda.
As school funding fluctuates annually and various initiatives are implemented based upon grants, governing bodies are unable to develop coherent approaches to staffing levels."
In Denbighshire, schools are retaining staff, who would previously have been put up for redeployment because of falling rolls, to help cover PPA time.
Newport also confirmed that falling rolls are being balanced out by the demands of workload reform, and expects the introduction of the foundation stage to lead to further growth.
A spokesperson said: "Teaching staff are likely to be broadly the same.
Falling rolls would have led to redundancies, but this is being off-set by the need for more staff to cover planning, preparation and assessment time for teachers.
"There has been a general increase in support staff hours and numbers in recent years as a result of the overall package of changes included in the teachers' workload agreement.
But Ceredigion noted that while the foundation stage and other initiatives may lead to rising demand for staff, extra funding would be required to fully implement them.