Those kids have been going to schools around there for years. There is no sense in using such police force to evict famlies with small children from their homes on property that they own.
The same schools that they have shown the nationwide highest truancy rates since these people bothered placing the kid names on the register?
Would you be keen to go to school regularly (or to send your children there) when a significant proportion of the school population (and the community they come from) have had it ingrained that your society is, to a person, scum?
there is another issue that strongly affects the truancy rates. When you tell an 11 year old traveller they are allowed to make all their own decisions about their life from now on - chances are they wont choose to stay at school. although it often works the other way too, with children being kept away from school as they can be more use at home.
So, there is a bit of a cultural thing about when you become and 'Adult' able to make your own decisions. This can isolate some traveller children from their peers as hey often have many more responsibilities at a young age compared to the average 11 year old.
this is coupled with a negative view of education within the culture due to years of racism, misunderstanding and often simple naivety (a lot of the current traveller parents/grandparents will not have attended school at all). luckily these attitudes are changing, albeit slowly
the problem is made worse by the lack of relevance for traveller children, but you could say that about a lot of kids.
i have a friend who worked with the local traveller community to encourage school attendance. the job was mainly split into educating parents about the benefits of education for their children's lifestyle, getting schools to understand that the students may have other responsibilities which prevent them from attending school all the time, and educating teachers about the needs and expectations of those students