Nineteen Palm Beach County elementary schools have to extend their school days this year after their students’ reading scores this spring ranked among the 300 lowest-performing elementaries in the state.

The number of county schools falling on the state’s Low 300 list of schools remains unchanged from last year, but the list includes three new names.

Joining the list this year are Starlight Cove Elementary, Rosenwald Elementary and Somerset Academy Lakes, a charter school.

Moving off the list are Grove Park, Northmore and Pioneer Park.

All 19 schools will extend their school day by at least 35 minutes.

State law requires that schools on the Low 300 list teach an extra hour of reading every day. Because the district’s schools already exceed the state’s minimum reading instruction time, the 17 district-operated schools on the list will extend their school day by just 35 minutes, a district spokeswoman said.

District leaders also are going to continue to extend the school day at three schools that are no longer on the Low 300 list: K.E. Cunningham/Canal Point Elementary, Pioneer Park Elementary and Washington Elementary.

Administrators say they sometimes maintain the extra time at schools that have risen off the list to avoid a yo-yo effect where schools that lose the extra time lose ground and fall back onto the list.

The state’s Low 300 list is made by combining each school’s average language-arts exam scores for the past three years and its average learning gains during the past three years.

The lowest 300 schools statewide end up on the list. This year, the list includes 301 schools since several scores had similar scores.

State lawmakers created the extended-day rule in 2012 so that students in schools with the biggest reading challenges would get more reading instruction.

The list initially included just the 100 lowest-performing elementary schools, but it was expanded for the 2014-15 school year to the bottom 300 schools.

The net benefits of the extra time aren’t completely clear, however.

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A 2016 school district study found that in the program's first three years, extended-day schools in most cases were associated with little or no significant progress, raising questions about how effective the extra reading time was.

Another point of criticism: The program also does nothing for struggling readers at schools that don't happen to fall onto the list.

And the law requires nearly all students at the affected schools to stay in school longer, even most students already reading on grade level, something that educators say makes it more difficult for them to target the weakest readers.

But many principals nonetheless say they find the extended school day useful and are disappointed when the extra time goes away.

The complete list of county schools on the Low 300 list this year is:

* Barton Elementary

* Belle Glade Elementary

* Dr. Mary Mcleod Bethune

* Glade View

* Gove

* Highland

* Indian Pines

* Lantana

* Lincoln

* Pahokee Elementary

* Pleasant City Elementary

* Rolling Green

* Roosevelt

* Rosenwald

* Somerset Academy Lakes

* South Grade

* Starlight Cove

* University Preparatory Academy Palm Beach

* West Riviera