A school district in Pennsylvania has banned the Girls Who Code book series for young readers, according to an index of banned books compiled by the free expression non-profit Pen America.

The books are four of more than 1,500 unique book titles that have been banned by schools across the country after conservative pushes to censor books. According to a report released by Pen America in April, 138 school districts across 32 states have banned books from their classrooms and school libraries.

A recent update to Pen America’s banned book index said the Central York school district last year banned the books The Friendship Code, Team BFF: Race to the Finish!, Lights, Music, Code! and Spotlight on Coding Club!. The school district has over 400 banned titles on the index.

A statement from officials in that district on Monday strongly denied that they had banned the book series.

“The information published in this article is categorically false,” the district’s statement said while linking to a Business Insider interview with the founder of Girls Who Code which reported the ban. “This book series not been banned, and they remain available in our libraries.”

The Central York district last year received national attention after it banned resource materials listed in 2020 by its diversity committee, including children’s books and documentaries. A coalition of students and parents successfully pushed the district to rescind its ban after public pressure.

In a statement explaining the ban of the diverse resources, the school district’s board president at the time, Jane Johnson, said: “What we are attempting to do is balance legitimate academic freedom with what could be literature/materials that are too activist in nature, and may lean more toward indoctrination rather than age-appropriate academic content.”

The Girls Who Code series features a group of girls who become friends in their school’s coding club. The series is in partnership with Girls Who Code, a non-profit that runs computer coding clubs and programming in schools for girls.

The CEO and founder of Girls Who Code, Reshma Saujani, expressed her anger over the series being banned.

“We use these stories to teach kids to code,” Saujani told Business Insider. “It felt very much like a direct attack on the movement we’ve been building to get girls coding.

“This is an opportunity to realize how big this movement is against our kids and how much we need to fight.”

Saujani said that the group Moms for Liberty, a conservative non-profit formed in 2021 that has been pushing book bans through local chapters across the country, was responsible for the Central York district’s ban on the series. The organization has advocated for banning books on race – including ones on the civil rights movement – and on LGBTQ+ themes, saying the volumes are “sexually explicit”, according to media watchdog Media Matters.

Aggressive campaigns to ban books in schools and libraries across the country have flared up over the culture wars of the last two years. While campaigns to ban books have always existed in the US, the movement gained momentum in 2021 when conservatives took aim at the academic “critical race” theory and turned it into a buzzword to stoke fears of liberal ideals being taught in classrooms.

According to Pen America’s banned books report, many of the titles being banned deal with LGBTQ+ themes or have non-white characters. The organization estimates that more than 300 groups, including local chapters of national organizations like Moms for Liberty, have been pushing for book bans. The groups have gained large traction through social media, where lists of titles have circulated.

The campaigns try to deflect accusations of racism and bigotry by claiming they are targeting material that is offensive or inappropriate for children.

Pen America estimates that 41% of banned books deal with LGBTQ+ themes while 40% have protagonists or secondary characters who are people of color.

An author of one of the Girls Who Code books, Jo Whittemore, said on Twitter: “Some people choose not to focus on how awesome and empowering and inspiring these books are but instead choose fear.”