be put through the mill

To be abused or treated very harshly; to suffer intense anguish, stress, or grief. I was put through the mill as a kid in high school. I couldn't get out of there fast enough. The coach was renowned for his strict practice regimen, and his players were put through the mill to become the toughest in the state.

through the mill, to go/to be put

To undergo hardship or rough treatment. The analogy here is to being ground down like grain. The figurative use of the term dates from the nineteenth century. “We’ve all passed through that mill,” wrote Rolf Bolderwood (A Colonial Reformer, 1890). A newer synonymous phrase, dating from the mid-1900s, is to put someone through the wringer, alluding to a wringer that squeezes moisture out of something. For example, “When they suspect child abuse, the police really put parents through the wringer.”