I don't think it's the amount that has been set that is unreasonable but to expect it done for the next day definitely is.
It's fine to have X hours of homework per week but there needs to be flexibility as to when the student does it.
What if you had theatre tickets for that night, or volunteering (which students are encouraged to do) or a part time job or hobby.
Over a week, with study periods and the weekend a student can fit it in. But that one particular night, that week, it might be impossible.