Sixteen students from Byrd and Tuckahoe middle schools in Henrico County have been charged with distributing and/or possessing the prescription drug Adderall, a psychostimulant used to treat attention deficit hyperactivity disorder. Henrico police have brought a total of 32 charges against the 16 students stemming from the distribution of the drug on April 24 and April 30, said Henrico police Lt. Gary Watson.