The suspects were arrested following an investigation into heroin distribution in Topton, Pa.
It also follows a number of heroin-related deaths, Berks County district attorney John Adams said in a news conference on Monday.
The students who were arrested were taken into custody at Brandywine Heights Area High School in Longswamp Township, Adams said.
One of those students, a 17-year-old girl, had heroin in her possession at the time of her arrest, investigators said.
Her name has not been released, but the 12 others who were arrested have been identified as:
Jesse Strain of Topton, Pa.
Carl Ritzman, of Temple, Pa.
Dylan Lesher of Mertztown, Pa.
Cameron Grace of Topton, Pa.
Brett Brugger of Topton, Pa.
Alexis Miller of Kempton, Pa.
Heather Gulick of Kutztown, Pa.
Ross Brugger of Topton, Pa.
Michael Moll of Macungie, Pa.
Logan Fenstermacher of Topton, Pa.
Ashley Hettrick of Mertztown, Pa.
Stephanie Oswald (no photo released)
The arrests come after a 4-month investigation by the district attorney's office and the Pennsylvania State Police. The investigation involved a number of undercover drug buys that ranged in price from $30 to $170, Adams said.