TAMPA, Fla. — Thousands of students headed back to school Monday as the school year opened in most Bay area counties. 

Students across Hillsborough, Hernando, Pasco, Polk, Manatee and Citrus counties all returned to class today. Pinellas students go back to school on Wednesday. 

It's a big day in Hillsborough County as returning students are seeing many changes, including building improvements and some new policies as district officials say safety remains a top priority. 

With a voter-approved referendum, students at almost two dozen schools will come back to new air conditions and other upgrades at their schools. 

And, for the first time ever, all Hillsborough County middle schools will have crossing guards. 

Also, Superintendent Jeff Eakins said every school is the district will have a new alert system in place at some point this year. 

The new system will be able to lock down a school in a matter if seconds. 

Teachers also will have badges that can trigger a visual and audio alert heard through the entire school. 

"We want to focus on what we know parents have been thinking a lot about - safety," said Eakins. "And we want to make sure we’re doing everything we can in using our tax payer dollars appropriately to ensure we have safe campuses and also have optimal conditions in classrooms."