Breaktime for some secondary teachers could be eaten up by travel as the skills-led 14-19 curriculum beds down, despite workload rules becoming stricter, a cross-party committee has been told.
But heads and assistants look likely to bear the brunt of tougher legislation, which will allow teachers to cover sick and absent colleagues for a minimal time only.
The Assembly's enterprise and learning committee has been investigating the effects of the 2003 workload agreement and is expected to report soon.
It could also suggest ways to ease the burden of the learning pathways, so that teachers do not spend breaks and planning, preparation and assessment time travelling between schools and colleges to teach.
It follows evidence to the committee from heads' representatives who say the travel requirements of the 14-19 pathways may mean teachers travelling during break and lunchtimes.
For the past few months the committee has been examining the workload deal, which was introduced to free teachers from clerical tasks and having to cover for absent colleagues, and to raise pupil achievement in England and Wales.
Some of the strongest evidence came from Paul Elliott, head of local government for Unison Cymru, which represents teaching assistants and school technicians. He said members had reported feeling "abused" under the agreement as teachers offloaded work on them.
Giving evidence to the committee, he said that teachers often delegated tasks - including teaching classes - to support staff, who did not receive extra pay for the duties.
Heads are also feeling the strain of having to cover for teachers. Iwan Guy, acting director of the National Association of Head Teachers Cymru, claimed pressure on them to enforce the deal was "a major reason (why) schools found it difficult to recruit and retain school leaders".