How was Amy punshed by Mr. Davis?

From the text:

"Your hand, Miss March!" was the only answer her mute appeal received, and too proud to cry or beseech, Amy set her teeth, threw back her head defiantly, and bore without flinching several tingling blows on her little palm. They were neither many nor heavy, but that made no difference to her. For the first time in her life she had been struck, and the disgrace, in her eyes, was as deep as if he had knocked her down.
"You will now stand on the platform till recess," said Mr. Davis, resolved to do the thing thoroughly, since he had begun.