In other words, the judge ordered the parents to not teach their own religion to their own child. This is clearly a violation of their First Ammendment rights.
This ruling was appealed and upheld. The family is continuing to appeal to a higher court. If they violate the judge's order, the child could be taken away and placed in a foster home.
Before you write this off as an isolated case, consider what precedents this might set. Suppose a judge in the future decides that your religion is not mainstream and should therefore be forbidden from your children? Texas has already decided that the Unitarian church is not enough of a religion to qualify for tax-exempt status. It's not a stretch to imagine a judge deciding to take away the children of Unitarian parents, based on this decision.