According to an arrest warrant, Cody Austin Beckett, put a "chemical agent" into Roseann Marie Monteleone's drink Thursday at the beginning of second period.
Police say the agent is believed to be a hand cleanser and it resulted in a severe medical reaction, producing lesions on Monteleone's throat. She also lost consciousness.
School officials say they suspected foul play and called police, who spent hours on campus interviewing students.
The investigation resulted in a charge of assault on a school employee. Police say Beckett is a student in one of Monteleone's morning classes and the motive is still unknown.
Monteleone was taken to Rex Hospital for treatment and released.
Beckett is scheduled to make a court appearance in June.