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I am sorry to hear about this situation. Technically, a parent can decide to leave the child with whomever they want. So they have the power to do so - something like sending the child off to boarding school.
However, just because they can does not mean that the decision may be challenged. The only way to really challenge this decision is to request a modification for custody, which is something that it sounds like you want to do, anyhow. Meaning, one would request modification to become the managing custodian.
A sample petition is HERE. Instructions on how to file are HERE.
If the Court agrees that this is "in the best interest of the child," then the Court will give you custody, and you can make the decisions as to place of residence and education of the child in most cases.
While the suit is pending, one may wish to file for temporary custody orders to get temporary custody.
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