Olathe ? A high school student accused of trying to poison his teacher’s drink pleaded guilty Wednesday to one felony count of making a criminal threat.

Trevor Hackl, 15, of the Kansas City suburb of Westwood, entered his plea in the juvenile division of Johnson County District Court and was placed on 18 months’ probation.

Prosecutors dropped a second count of making a criminal threat, stemming from a previous incident, as part of a plea agreement.

Hackl had been accused of telling fellow students at Shawnee Mission East High School in Prairie Village on Jan. 27 that he planned to put something in his teacher’s drink. That same day, prosecutors say, the teacher said his glass of water smelled and tasted bad.

In court Wednesday, Hackl said he put copper sulfate in the drink. The substance – sometimes used in science lab classes – can be toxic, causing nausea and shock to the brain and internal organs.

The teacher was not injured.

The other felony count had alleged that on Dec. 1, Hackl passed another student a note threatening a different teacher and that teacher’s family.

In addition to placing Hackl on probation, District Judge Brenda Cameron ordered him to write a letter of apology to the teacher whose drink he tainted. Hackl also was ordered to remain under house arrest until he begins counseling and to follow the recommendations of his psychological evaluation.

He was released last week from juvenile detention.

“You do seem like a young man who has a lot going for you,” the judge said, “and I hope you can get things turned around.”