Experts said that the sharp increase in threats and false alarms in the days since the Florida shooting reflects the unusually intense public conversation and media coverage that have unfolded since that attack. In the tense days that have followed, the experts said, teenagers are borrowing the language of school shootings to provoke or cause turmoil. And anxious school employees are on high alert, watchful for any sign of a potential shooter and quick to summon the police over behavior that, in a different moment, might have been overlooked.

Florida had at least 31 incidents in the week after the shooting, more than any other state, the group said; Ohio followed, with 29; and Kentucky was third, with 24. Other states that experienced unusually high numbers of threats, false alarms or other incidents included California, Georgia, Mississippi, New York, Texas and Virginia.

Dozens of teenagers have been arrested in connection with threats, often posted on Twitter or Snapchat. School administrators are scrutinizing students and their backpacks closely; the day after the Florida attack, a student at Clarksburg High School in Montgomery County, Md., was found to have a loaded Glock 9-millimeter handgun in his bag at school, the police said. A student at Pasco High School in Dade City, Fla., was arrested on Friday after a staff member conducting a routine sweep of vehicles in the parking lot discovered an AR-15 rifle and ammunition in the student’s truck. (The school district later said that the gun apparently had been meant for hog hunting.)

The police say they are taking all reports seriously in light of the attack in Florida, where law enforcement authorities had been given warnings about the suspect who is accused of fatally shooting 17 people at Marjory Stoneman Douglas High School.

Scott Israel, the sheriff of Broward County, Fla., said on Thursday that his department had received 23 calls regarding the suspect, Nikolas Cruz, over several years, but may not have followed up on them sufficiently. On Jan. 5, a woman who knew Mr. Cruz called the F.B.I.’s tip hotline saying that she was worried he might resort to slipping “into a school and just shooting the place up.” In that call, made more than a month before the attack, she gave the authorities an unambiguous warning: “I know he’s going to explode.”