The short answer
The question isn't usually whether a reading pen would help a struggling reader, for most students who need one that's already clear. The question that actually stalls the process is who pays for it, and how a district or a family gets from "this would help" to a device in the student's hands.
For a student with a documented disability and an IEP or 504 plan, assistive technology, including reading pens, is legally the school's responsibility to provide if it's required for the student to access their education, at no cost to the family. That's federal law under IDEA for IEPs and under Section 504 of the Rehabilitation Act for 504 plans.
Three paths to funding
Individual IEP or 504 plan: assistive technology is added through an evaluation showing the need, documented in the plan, and then provided by the district. What actually needs to happen: the need is identified, usually by a special education teacher, a reading specialist, or a formal assistive technology evaluation; it's written into the IEP or 504 plan specifically, not just discussed verbally; and the district procures the device, typically through the special education department's budget.
District or school-wide purchasing: some districts buy reading pens at scale, for a resource room, a whole grade level, or a school-wide accessibility program, rather than one device per individual IEP. District e-procurement platforms let a district manage bulk purchasing and track which devices are assigned to which programs or students.
Parent-funded, outside the school system: for a family whose child doesn't have or doesn't want a formal IEP or 504 evaluation, direct purchase is the third path. Some private insurance plans and state vocational rehabilitation programs cover assistive technology in specific circumstances.
Writing the need into an IEP or 504 plan
The single biggest reason assistive technology requests stall isn't budget, it's vague documentation. What holds up: a specific, observed barrier, such as a student who demonstrates grade-level listening comprehension but reads below level on decoding assessments; a specific accommodation requested, such as access to a text-to-speech reading device for worksheets, textbooks, and printed assessments; and language tied to an assessment or evaluation, not just a teacher's informal observation.
Budget categories that commonly cover this
Special education or IDEA Part B funds for students with an IEP; Section 504 accommodation budgets, separate from IEP funding in most districts and often underused; Title I or Title III funds, with Title III covering English language learner support even without a disability designation; and general accessibility or assistive technology grants from states and foundations.