Parents, teachers and members of the Irish National Teachers Organisation (INTO) will deliver a letter to the Education Minister following a protest over class sizes in Dublin today.
The demonstration is being organised to urge Ruairi Quinn to protect primary education in the upcoming Budget.
Union members will address today's rally at the Department of Education offices.
The President of the INTO, Brendan O'Sullivan, is encouraging those from Dublin, Louth, Meath, Kildare and Wicklow - which are affected by some of the most overcrowded classes in the country - to attend.
"There is always a choice," Mr O'Sullivan said.
"A decision to balance the books on the backs of our children in primary schools is already a choice - it's not a neutral or an inevitable position.
"There are other choices we could make."