Members of the Oireachtas Education Committee have visited a school being threatened with closure to see the facilities that could be lost to local children.
Three-hundred boys from the De La Salle National School in Ballyfermot are set to be transferred to a nearby campus with more than 1,000 pupils.
Under the proposal, the children will be moved into the Dominican schools - St Gabriel's, St Michael's and St Raphael's.
But parents have pleaded with Archbishop Diarmuid Martin to reverse the decision.
Martin Walsh, the spokesperson for the De La Salle Parents' Association, fears that if the local school amalgamation goes ahead it could see over 1,000 children squeezed into half the space they usually enjoy.
"We'll be losing resources in all four schools," said Mr Walsh.
"Education Committee members including Joanna Tuffy, Aengus O Snodaigh and Michael Conaghan attended the schools because of the public backlash against the proposed closures.
"They were able to ask their own questions such as would 320 pre-school and after-school places be kept open, the answer to which was 'no'," he added.
Parents argue that their children will lose the use of a new building at De La Salle that was built just under two years ago. It is currently used for a breakfast club. They are also concerned about the sports ground.
A spokeswoman for the Dublin Diocese has said that the decision to merge the school was due to falling numbers, but this is disputed by parents who say CSO figures show otherwise.
The spokeswoman also referred to the resources available to the students after the amalgamation.
"Pupils will still have use of the GAA pitch at De La Salle. Homework and breakfast clubs are available in the Dominican schools," she said.