When parents have joint legal custody of their children that means that on matters such as education and medical issues the parents must “agree” on these type of decisions. One parent cannot change the school where the children attend without the permission of the other parent. Similarly, one parent cannot change the medical doctors the children regularly see without the other spouses consent.
In order to protect your legal rights you need to immediately retain an experienced child custody lawyer who will likely send a formal letter to your spouse advising her that she has violated the court order and to demand that she remove the children from the new school or in the alternative take steps to inform you as to why she made this decision. The same is required of her as it relates to informing you of why she changed pediatricians. If you do not agree then the matter can hopefully be “mediated” and if not then you will need to bring a court action to protect your legal rights.