Parents of autistic children claim the youngsters have missed out on use of a school playground because there have not been enough supervision staff.
They said the roll at Caithness Early Years Autism Centre (CEYAC) has increased, but staff numbers have not changed to keep pace with this.
Highland Council said the situation at CEYAC was under review.
Maureen Stockdale, whose son Joseph attends the unit, said the children need to be able to go out and play.
She said: "Can you imagine having to sit in a classroom with lots and lots of energy and to look out the window at other children playing and you are not able to go out and play?'
"School is the perfect environment for a child to play, to learn through play, to socialise, to be part of something and these children are being discriminated against because they are not allowed to get out there.
"Donnie MacDonald, acting director of education, culture and sport, said the matter was part of an ongoing review.
He said: "As a result of recent discussions and pending the outcomes of the above review, the council has agreed to additional time being allocated to support staffing in CEYAC."
This will be put in place as soon as possible in order to ensure that pupils attending CEYAC have appropriate access to the curriculum and outdoor play facilities."