The short answer
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. The complexity isn't whether the school can pay, it's getting the need documented and the purchase processed.
Three paths to funding
Individual IEP or 504 plan: assistive technology is added the same way any other accommodation is, through an evaluation showing the need, documented in the plan itself, and then provided by the district. The device becomes part of what the school is obligated to supply, not something the family purchases and gets reimbursed for.
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. This is common where a district has a large population of students who'd benefit, since per-student procurement is slower and more expensive than a bulk purchase. District e-procurement platforms let a district manage bulk purchasing and track which devices are assigned to which programs or students, which matters for both budget reporting and equipment accountability.
Parent-funded, outside the school system: for a family whose child doesn't have or doesn't want a formal IEP or 504 evaluation, or who wants a device for home use independent of what the school provides, direct purchase is the third path. Some private insurance plans and state vocational rehabilitation programs cover assistive technology in specific circumstances, so it's worth checking both before assuming the full cost falls on the family.
Writing the need into an IEP or 504 plan
The single biggest reason assistive technology requests stall isn't budget, it's vague documentation. "Would benefit from reading support" is not the same as language an IEP team can act on.
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 printed materials; and language tied to an assessment or evaluation rather than just a teacher's informal observation, which is what makes the request defensible if it's ever questioned.
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 simply because fewer staff know it exists; Title I or Title III funds, with Title III specifically for English language learner support, which can cover reading technology used for ESL students even without a disability designation; and general accessibility or assistive technology grants, since many states and some foundations fund AT purchases directly.