Teresa Gilmete Badger, 47, was arrested and booked into the Solano County Jail on three felony counts of food poisoning Friday.
Benicia police say several teachers from Matthew Turner Elementary School were rushed to the hospital following the dinner at a private home on Nov. 21.
Blood work on one of the patients confirmed the presence of THC, an active ingredient in marijuana.
Police say Badger was the one who laced the food.
The motive for the incident remains unknown.
The Associated Press contributed to this report.