There are schools that are much more oriented (or have programs that are much more oriented) towards people who are working or are otherwise not attending school full time. I'm not sure I can really fault the average undergrad program for orienting things towards the 95% case situation. (Some schools are also much more commuter-oriented than others are.)
You are absolutely right and that definitely makes sense. But, and I have to preface this has been my experience, there are virtually no accommodations. School is your job when you go back to a university and colleges believe that is what you should be doing.
Now to the legalities. The Age Discrimination Act mandates any institution receiving federal funding from preventing someone from being able to participate[0]. So like a physical disability, if you only make stairs because "99% of people can walk" but cannot accommodate for someone in a wheelchair, you would be in violation of the Americans with Disabilities Act. Same thing with making a website accessible to the blind. By making your courses only available during business hours, you essentially are telling working adults "we are preventing you from participating in mandatory courses because you cannot be at work during the class." Work, mind you, that will pay their bills, support their family, and keep them out of absurd debt bondage upon graduation.
When you make class at 8AM for 1.5 hours, Monday-Wednesday-Friday, you are discriminating against working adults. It doesn't matter if the discrimination is intentional. Your very allowance of not offering a course wholly online without a mandatory attended lecture or just a night class is pure evidence that you do not want non-traditional students. How can an college believe that someone who works full time can make that work? Night classes are at least an accommodation and can work.
What I've found is technical colleges, since they're catered toward people going back to school, they do a much better job all around. Also since they are city funded and not a state run university through tax payers, they can hire real employees. So when I ask an administrative question that is very important, I don't get "uh I'm not sure, let me ask a staff member since I'm only a student employee! Can you hold for 10 minutes?"
It may be discrimination towards people with jobs, but it's not based on age. Legally, employees are not a protected class. Also, the protected class for age is "people over 40", who are not necessarily more likely to work full time than people under 40.
If you intentionally create an environment that is hostile toward people of differing ages, you are discriminating. My college required me upon sign up to put in for my housing "My parent/guardians contact information." Universally everyone is an adult when they enter college (the people who don't are so rare I'm ignoring them). I could not leave the page unless I entered any data so I just put my name and contact info. Guess what else? All the events are catered toward young students and target them specifically that way. If someone really wanted to, they could easily have an age discrimination case against almost every school. Culturally however, people don't because they don't want to associate with lesser experienced and more incredibly arrogant individuals.
