MANHATTAN, N.Y. (PIX11) – A preschool in New York City's Upper West Side faces questions after a substitute teacher, who's transgender, read a children's book about trans inclusivity to a class of three- and four-year-olds. Now, the preschool lesson is dividing parents and educators at the city-funded New York Kids Club on Amsterdam Avenue in Manhattan. “Most of the parents were in shock and clueless of the decision that the school made,” parent Vivian Cialini said. The 10 best films of 2024: 'Nosferatu,' 'The Brutalist,' and more Cialini’s three-year-old son was in the class where the substitute teacher recently read Theresa Thorn's “It Feels Good to Be Yourself: A Book about Gender Identity” to a class of 16 students. Some of the kids reportedly came home with questions and parents started to debate whether the book exploring gender is age-appropriate.  Per the book's publisher, Henry Holt and Co., the picture book aims to introduce the concept of gender identity to kids using "child-friendly language" and give both children and parents the tools to approach the subject with care. The 40-page book, which was released in 2019, is recommended for ages 4-8. "It Feels Good to be Yourself" by Theresa Thorn (Courtesy of Macmillan US) One excerpt reads, “There are so many ways to be a boy or girl. Not everyone feels like either a boy or a girl.” Cialini says she believes it's too early for children this age to understand what they're being exposed to. The mother added: "They barely have awareness of their [own] body." In a statement to PIX11, New York Kids Club’s CEO Jennifer Clement said: "We are deeply committed to fostering an environment where children can grow, learn, and explore in a manner that is both age-appropriate and respectful of diverse perspectives." The statement also said the school is working to “ensure that materials utilized align with the developmental needs of our students." In a separate email to parents, the administration stressed the importance of teaching inclusion to all students, writing, “We all agree that we would rather this have been communicated to our families beforehand and will ensure it takes place in the future.” Hundreds of animals killed in Dallas shopping center fire Alaina Daniels helped start Transformative Schools, an afternoon program for trans, queer, and non-binary students beginning at age nine. “The message of the book is: It’s OK to be whatever gender you’d like to be," said Daniels.  She added that it’s healthy for children to ask questions and explore who they are from a young age. “These are conversations kids and adults should be having and should be learning,” Daniels said. Cialini says she believes in acceptance and inclusion but also transparency. She says the school "violated our rights as parents" by not asking permission first. In a statement, NYC Public Schools said it values using age-appropriate and inclusive curriculum that will benefit students' development and social-emotional growth. The school system added that it's "engaging with this specific program to understand how the material was introduced and whether it adhered to the recommended guidelines." Days will get longer in January: Which cities will gain the most daylight? Children and gender identity: What's the research say? While there's still much research to be done into the concept of gender identity as it relates to child development, much current research indicates that children become aware of gender dysphoria — that is the feeling of distress one might feel when their gender identity differs from their sex assigned at birth — much earlier than parents might suspect. June 2020 research out of Cedars-Sinai found that out of 210 transgender adults, 73% of transgender women and 78% of transgender men first experienced gender dysphoria by age 7. Meanwhile, April 2023 research published in the peer-reviewed BJPsych Bulletin by Cambridge University Press found that children are typically aware of gender dysphoria by age 5. Additionally, one noted study published by the American Academy of Pediatrics also found that 94% of transgender youths (out of 317 youths studied) still identified as transgender five years after their initial social transition. The research found that while "retransitioning" happens for some children, it's not very common.