If at least one of the parents has French nationality and the child is registered at the consulate, you can apply for a grant: every year.  The grant commission in Dublin sits in spring for the following school year.  If your situation has changed or you were not able to apply in time because you arrived in Ireland recently, there is a second commission in October.  In both cases, the school will always inform you of the dates of the commissions and provide you with the application papers.