Too often public schools do not have, within their educational structure, someone who is trained to provide direct one to one tutoring, nor do they have the staffing to provide such.
Tutoring is typically provided at least one period per day if the child attends a private special education school, such as one of the Orton-Gillingham based (reading) programs around the country. This period of tutoring is not viewed as either an accommodation or modification, but a direct educational service.
Tutoring and/or direct one to one remediation of a required academic skill, such as reading, is clearly supported in IDEA 2004.
If you do not have an IEP, I think it can be argued as necessary as part of a 504 Plan in that the child needs to be taught how to read in order to be able to access the curriculum in the same manner as typical non special education, regular education children.