Two library groups are urging the county council to rethink its decision to close the School Library Service.
The Charted Institute of Library & Information Professionals (CILIP) and the School Library Association (SLA) are calling for Hertfordshire County Council to review its decision to close the service on March 31.
The council came to its conclusion in December, stating there was "decreasing demand" for the service, which provides mobile libraries, books and professional help to schools.
But the CILIP and the SLA are calling on headteachers in Hertfordshire to back the service and ask the council to reconsider the decision.
Annie Mauger, chief executive of CILIP said: “I am incredibly concerned about the impact that the closure will have on children’s education and attainment.
"The service has a well-deserved reputation for excellence and its closure will be a blow to hundreds of schools and thousands of children across Hertfordshire."