A popular claim made by many Christian Nationalists is that the absence of any explicit endorsement of their religion by public schools - or indeed by government generally - represents an expression of hostility towards their religion. In particular, it is their position that the failure of schools to promote creationism, Bible reading, Christian prayers, and other examples of Christian beliefs means that the schools are effectively denigrating those beliefs.
Thus the fact that schools don't explicitly endorse Jesus, either through images of Jesus hanging in schools or in school lessons, is treated as though schools were actually trying to take Jesus away from children. This is the example represented in the above image, taken originally from World War II poster of a girl holding a picture of her father and imploring people not to "kill her daddy with careless talk."
The very idea that schools are taking Jesus away from children by not explicitly promoting Jesus to them is absurd. There are lots of things which schools do not explicitly endorse or promote, but this cannot be construed as an effort to denigrate or undermine them. Schools obviously don't promote other religions like Buddhism or Hinduism, so does this mean that they are trying to undermine those religions? Schools generally don't promote any particular liberal or conservative political doctrines, so does this mean that the schools are trying to attack those doctrines?
Of course not - I don't think that there is any other segment of society where such claims are made and such beliefs promoted. There are far more things which the government and government institutions don't promote than they do promote, but no one actually believes that the government is therefore attacking all those beliefs. At worst people might despair over the neglect of their favorite causes, but that's about it. Only Christian Nationalists have gotten the idea that the absence of endorsement is the presence of hostility.