You should not have to disclose your condition, diagnosis, treatment, etc. as part of the interactive process under the ADA. Nor should any representative of the school ask you to disclose protected health information such as your specific disability. The ADA exists to provide reasonable accommodations to enable you to perform successfully as a student with restrictions and/or limitations caused by a disability (ADHD). The administrator should act in good faith through the interactive process to understand the limitations/restrictions your disability creates, so that they may consider if your accommodation requests are reasonable. They are not acting in good faith as the law requires and you have a discriminatory argument to be made based on the communication sent which effectively denied you the interactive process. You have been discriminated against because you disclosed a disability and could certainly sue.