Okay kiddo, so do you know what a catholic school is? It's like a school where boys and girls can go to learn and study about different things, just like your school. But in catholic schools, they also learn about God and Jesus and talk about how to be good people.
Now, sometimes these schools come together to form a group called the Association of Catholic Colleges and Universities (ACCU). This means that they work together to help each other out and to make sure that they are all following the same rules and values.
So it's like when you and your friends work together on a school project. You help each other out and make sure you all do a good job. That's what the ACCU does for these schools. They help each other out so that they can be the best catholic schools they can be.