Almost two thirds of special schools are not participating in a summer education scheme aimed at supporting children with disabilities and others who have struggled more than most as a result of the recent school closures.
Just 48 special schools have registered their interest with the Department of Education in running a programme, out of a total of 134.
Last year, just 35 special schools ran programmes.
A representative of the sector has told RTÉ News that information on the summer programmes came too late for many schools.
The representative said that by the time schools were notified many staff had already made arrangements for holidays and some schools have found it impossible to source the staff needed to run programmes.
Lorraine Dempsey of disability organisation Inclusion Ireland said this year was "yet another year of disappointment for children with the most complex needs, who invariably are the ones who most need an extended school year".
Ms Dempsey said that Inclusion Ireland had warned in May of 2020 that summer programmes were going to fail unless plans were announced early enough for schools to make arrangements.
Yesterday, the Department of Education published preliminary figures which showed a total of almost 1,000 schools across the country have registered an interest running summer programmes.
They include mainstream primary and second level schools, as well as special schools.
But the department said data on actual participation will only become known after the summer.