Frank Thompson, 57, has been charged with multiple drug-related offences stemming from the incident, according to a statement from the Westfield Police Department.
Students at Roosevelt Intermediate School found the teacher unconscious on the classroom floor around 9am on 29 November.
According to the police statement, students noted the teacher was "in distress" and found a school administrator to help.
A school resource officer named Fortunato Riga responded to the scene and noticed that Mr Thompson was allegedly showing signs of a drug overdose.
Mr Riga provided an emergency dose of Narcan, a medication that helps reverse opioid overdoses, which resulted in an improvement in Mr Thompson’s condition, according to police.
An investigation was launched following the incident, which found that Mr Thompson was allegedly keeping "suspected controlled dangerous substances and various items of drug paraphernalia" in his classroom closet, according to the statement.
Mr Thompson was charged on 5 January with possession of controlled dangerous substance, possession of drug paraphernalia, and endangering welfare of children.
It’s currently unclear if Mr Thompson is still employed at the school.
Superintendent Raymond Gonzalez told PEOPLE that "personnel matters are … deemed confidential."
"Appropriate action was taken by the administration of the Westfield Public Schools in accordance with the laws and regulations governing school personnel and this particular situation," he told the outlet. "Since this is also an on-going police matter, it would be inappropriate for the school administration to comment any further at this time."
He went on to say that the "safety and welfare of our students and staff is of utmost importance" to the administration and district.
Mr Thompson is scheduled to appear in court on 1 February. It is unclear if he has entered a plea to his charges at this time.