It is always a student's right, and personal choice, to determine if they chose to disclose their disability to the Office of Disability Services. Disclosing your disability can be done at any point in the semester, and does not require that accommodations be used.
Accommodations cannot be given retroactively if a student makes the choice not to disclose their disability to the Office of Disability Services. Alternatively, if a student does disclose their disability but does not request that letters of accommodations be sent to their professor, accommodations will not be granted.
The Office of Disability services cannot retroactively give accommodations if a student does not disclose their disability to the Office of Disability Services, or request that letters of accommodation be sent, even in the case that the students feels work submitted or exam scores received do not accurately reflect their abilities.