There's nothing ominous about the statement.
Why the scare quotes? Aren't you on a medical leave?Quoting collegeADA
Your failure to respond to the email triggers this language: "if you do not respond, you may be ineligible to request readmission". You have now been informed of the terms for readmission.
We can't read the correspondence from here, but you have suggested that the college wanted neuropsychological testing and documentation of your psychological progress and that you chose not to provide the latter. Why would they want to set you up for a repeat performance of the mental breakdown that led to your prior withdrawal? Also, colleges have heightened concern these days over whether students they admit pose a potential risk of harm to themselves or others.Quoting collegeADA
You were denied readdmission, as you were warned could happen, because you failed to document that you were sufficiently recovered from your mental illness to successfully and safely continue your course of study. You were not "denied access to a college education" - there are colleges all over the nation, and you can apply to any one that you choose.Quoting collegeADA
Provisions limited to employers would only apply to colleges if you work for them. Also, "After a person starts work, a medical examination or inquiry of an employee must be job-related and consistent with business necessity. Employers may conduct employee medical examinations where there is evidence of a job performance or safety problem, examinations required by other Federal laws, examinations to determine current oefitnessî to perform a particular job, and voluntary examinations that are part of employee health programs."Quoting collegeADA
No, you weren't. You were denied readmission to a college because you failed to comply with their notice instructing you of the steps you needed to take to regain readmission, and refused to document that you were sufficiently recovered from your mental illness that you would not simply repeat the events that led to your prior withdrawal.Quoting collegeADA
The extra time, for certain disabilities, is deemed a "reasonable accommodation". There's nothing reasonable about your expectation that the college will ignore your past history of mental illness when considering your application for readmission.Quoting collegeADA
You are confused about the legal implications of the notice you received. As it explicitly stated, your lack of cooperation could make you ineligible for readmission. The college has told you what you need to do to be readmitted, and you are refusing to take those steps. You are bringing this outcome on yourself.Quoting collegeADA
From what you've told us so far, at least to the extent of what a court might order, probably nothing. You have given us no basis to believe that the college's demands are unreasonable, and have provided no explanation for your refusal to comply with their conditions for readmission. Perhaps there are some important facts you left out?Quoting collegeADA
The one has nothing to do with the other.Quoting collegeADA
Why do you believe that their request that you document recovery from your mental breakdown, to an extent sufficient to enable you to complete a course of study, is an ADA violation? If it bears repeating, you're not an employee and your impression about what can be demanded of employees is incorrect.Quoting collegeADA

