LAKELAND — Law enforcement agencies across Polk County increased patrols at schools Thursday following the deadliest school shooting in the U.S. in the past five years.

Parents can expect an increased presence Friday as well.

The heightened patrols come a day after 17 people were killed and 14 wounded at Marjory Stoneman Douglas High School in Parkland. Nikolas Cruz, 19, has been charged with 17 counts of premeditated murder.

Lakeland police spokesman Gary Gross said the agency doubled its number of officers at schools Thursday morning and added more Thursday afternoon during dismissal.

Traffic units were directed to drive through campuses on a regular basis, while school-resource officers were told to talk to students about reporting any type of suspicious behavior.

Jamie Brown, a spokeswoman for the Winter Haven Police Department, said additional officers will be at Winter Haven schools Friday morning.

The Polk County Sheriff's Office declined to release information about strategies for improving campus security.

The Sheriff's Office issued a Twitter message Thursday morning saying it is joining other agencies across the state in increasing the number of officers in schools "to try to provide some peace of mind to parents everywhere."

Students showed up for class as usual Thursday, with no noticeable drop in attendance, though Polk's public school system put a number of measures in place to address the aftermath of Wednesday's shooting in Parkland.

Polk School District Superintendent Jacqueline Byrd wrote on Facebook that grief counselors are available for students who need help.

District counselors, psychologists and social workers also are conducting assessments of students who have previously made threats that involved a risk of violence, Byrd wrote, adding that a system is in place to monitor any threats of violence or bullying on district-issued email addresses and documents stored on the district's domain.

Byrd addressed the shooting and any action the district has taken to prepare for or prevent any attacks on campus.

She mentioned regular lockdowns and "run, hide and fight" drills to respond to different scenarios, including active shooters. School-resource officers also teach students to report any suspicious activity or security concerns to staff members.

"Additionally, we continually make safety upgrades, including fencing and single-entry/buzzer systems, at our more than 150 school sites," Byrd wrote. "We prioritize facilities projects that will ensure a greater level of safety for our students and employees."

Eric Pera can be reached at eric.pera@theledger.com or 863-802-7528. John Chambliss can be reached at john.chambliss@theledger.com or 863-802-7588.