Most parents begin searching for a place for their children when they are in the 5th year of school, with the majority part of their "action" taking place once the child enters Year 6, the sixth year of primary school.
Before you do anything else, it is essential to know the process of registration in the grinds of Ireland. You can contact at https://ashfieldcollege.ie/our-grinds/ for private grinds in Ireland. The school or learn via their website where you can obtain the registration form and when the deadline of admission. Private schools may not have formal registrations in this sense, however, it's worth looking into it earlier in the school year.
The fees for registration vary and can be in the hundreds of dollars. It is important to apply and apply as soon as you can since the majority of private schools end their waiting lists prior to the deadline for admission; however regardless, even if you're not in the running, you might still have a chance don't put too much faith on it, however, you might be able to accept the late application, especially when academic standards haven't been met by other students who are applying for admission to the institution.
A lot of schools conduct interviews with both the child and the parent in order to examine each of them individually and then decide if they're suitable for their school. However, don't worry about it, it isn't as difficult as it may sound.