Norma Anne Watson, the GTC's new convener, had reported to an earlier meeting of a council committee that she had not been reassured by suggestions from the Scottish Office that assistants should be allowed to do "low level marking".
Mrs Watson is a member of the Government steering group which plans to issue guidance to the education authorities next month on the use of assistants.
Gordon Kirk, the GTC's vice-convener, reflected general concern that the initiative was "a clear dilutionary measure".
Professor Kirk also feared that classroom assistants could be used in future to drive down the number of student teachers entering training.
But Mrs Watson said at last week's meeting that she was now "more comfortable" with the provision of assistants following a meeting of the national steering group a fortnight ago. "The key to making the relationship between teachers and assistants work will be whether they have enough time to liaise with each other or not," Mrs Watson said.
She told The TES Scotland later: "The fears are still there about the dilution of teacher professionalism, although we have had assurances in the steering group that that is not the aim. Although I am comfortable with the guidance that is likely to go out to councils, it is the operational side of things that matters.
"What we don't want are 32 councils doing their own thing. That's not good for the people doing the job or for staff moving between one authority and another."