South El Monte, California, parents were shocked to learn last week that a teacher at a day care facility allegedly applied mood-calming stickers known as "Zen Patches" on preschoolers without the parents’ consent.

FOX 11 Los Angeles reported that parents of students at Options for Learning Head Start were outraged and are now demanding teacher accountability and child safety.

Two of the children affected by the patches, a 3-year-old and 4-year-old, told officials about the placement of the patches in interviews.

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Head Start South El Monte

A teacher at the Options for Learning Head Start facility in South El Monte, Calif., was fired after allegedly applying mood-calming stickers to preschoolers. (Google Maps)

Meanwhile, parents expressed their dismay about the situation to the station, reporting that stickers were placed on every child in the classroom, then removed before the students were dismissed for the day.

"We were surprised and really upset because you bring your kids, and you expect it to be good, you know," parent Vicky Cano told the news station.

The news broke when a mother of one of the preschoolers showed up unannounced at the school, where a teacher allegedly used mood-calming patches to control the children and make them sleepy.

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child plays with wooden cubes with colorful letters

A teacher at a South El Monte, Calif., preschool allegedly gave mood-calming stickers to students and removed the stickers before the students were dismissed. (iStock)

Parents also became suspicious when their children began to display behavioral changes and disruptions in their sleeping patterns.

Dr. Daniel Turner-Lloveras, a physician, told FOX 11 about the potential risks associated with applying any type of substance to children without the consent of parents.

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children coloring

Parents were outraged after learning a teacher at a South El Monte, Calif., preschool allegedly gave their children mood-calming stickers. (iStock)

He emphasized that the children could have suffered adverse effects, such as allergic reactions, while also highlighting the lack of formal regulation for these types of products.

Fox News Digital reached out to the school and Options for Learning Head Start, but did not immediately hear back.

Options for Learning Head Start CEO Paul F. Pulver said in a statement provided to FOX 11 that an internal review of the incident in South El Monte confirmed that the "aromatic stickers were given to a limited number of students," adding it was a class of 16 students.

Pulver also said, "their distribution violated our policy requiring parental decision-making and consent on all such matters. The employee who provided the stickers has been fired."

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Despite the teacher being fired, parents of the students told FOX 11 they want more.

"Firing her is not good enough at all," Stephanie Rodriguez told the news station. "I want justice. She should be in jail."