Two separate countries.
That would not the responsibility of the school, besides plenty of children would leave a school to move to another there wouldn't be the resources to check them all. I did it with my dc as I moved homes.
This is on Tusla, reaching out to SE in NI although I'm not sure if that would be legal due to GDPR.
Tusla are consistent with saying they were providing support and not involved. Not sure the difference tbh.
Tusla dropped the ball especially if the story about a different child being presented to a meeting and Tusla employee had no clue. However in saying that SE are overworked, burn out and a child could have several SW over a period. Without an updated picture of child, (a lot of files have no pictures of children) it would be simple enough to pull off.
Terrifying how simple it is to have an abused child slip through Tusla net.