Thousands of protesting teachers have warned they will fight further education cuts that target the most vulnerable.
Students and newly qualified men and women also joined the rally at the Dail to demand equal pay for equal work after the government slashed their starting salaries.
Gerry Breslin, president of second-level school union Asti, told about 2,000 supporters that education cuts affect children and young people's lives today and in the future.
"They affect student well-being and student attainment," he said.
"They hinder economic recovery. They hurt the vulnerable the most.
"Our children, our young people, our young teachers are being hurt. It is essential that we send a clear message today. There can be no more cuts to education."
Anne Fay, president of the Irish National Teachers' Organisation (INTO), said primary schools were already on the breadline.
"Education funding has fallen off a cliff in recent years while the system is coping with more and more pupils every year," she said.
"The school system is at breaking point and we need to send a message to government today that education cuts don't heal."
The unions - backed by several politicians - criticised failings to tackle teacher unemployment and cuts to the pay of new teachers and allowances of others.