What is the current state of the law in the United States on the authority of a teacher to inflict severe punishment on a minor?

The leading case in the United States is State v. Pendergrass, supra. The judgment in that case in part reads as follows: It is not easy to state with precision the powers which the law grants to school masters with respect to the correction of their pupils. It is analogous to that which belongs to parents, and the authority of the teacher is regarded as a delegation of parental authority. One of the most sacred duties of parents is to train up and qualify their children for becoming useful and virtuous members of society; this duty cannot be effectually performed without the ability to command obedience, to control stubbornness, to quicken diligence, to reform bad habits; and to enable him to exercise this salutary sway he is armed with the power to administer moderate correction, when he shall believe it to be just and necessary. The teacher, as the substitute of the parent, is charged in part with the performance of his duties, and in the exercise of these delegated duties is invested with his power. The law has not undertaken to prescribe stated punishments for particular offences, but has contented itself with the general grant of the power of moderate correction, and has confided the graduation of punishment within the limits of this grant to the discretion of the teacher. The line which separates moderate correction from immoderate punishment can only be ascertained by reference to general principles. The welfare of the child is the main purpose for which pain is permitted to be inflicted. Any punishment, therefore, which may seriously endanger life, limbs, or health, or shall disfigure the child, or cause any other permanent injury, may be pronounced in itself immoderate, as not only being unnecessary for, but inconsistent with the purpose for which correction is authorized. But any correction, however severe, which produces temporary pain and no permanent ill, cannot be so pronounced, since it may have been necessary for the reformation of the child, and does not injuriously affect its future welfare.