I think the focus of teaching should be students' learning,
and all policies including late assignment policies should be designed with
the goal of improving student learning and experience.
A good fair policy would encourage learning and good behavior,
a bad unfair one would do the opposite.
I think students generally care too much about grades,
it is important to refocus them as much as possible on learning.
Assignments, tests, and grades are tools for teachings not goals of teaching.
The hard deadline policy is common but
I think it is also a common experience of instructors that
it doesn't work well.
It is important to think about why it is so,
if we understand why hard deadlines do not work well
then we can design better policies.
In my experience,
the followings are the main reasons for missing deadlines in most cases
(roughly based on the justifications my students gave me
when asking for extensions in my previous courses):
small unexpected submission difficulties,
i.e. they have finished assignments but
they were unable to submit it before deadline,
e.g. they lost power just before deadline.
Considerable number of students leave working on assignments to the last minute.
They are also not good with estimating the time they need to finish assignments.
So they go over deadline.
events beyond students' reasonable control prevented them from finishing assignments, e.g. serious illness.
Of course we would not want to penalized students for the 3rd reason.
But we should also try to help those in the first two groups.
One common alternative to hard deadlines is having grace days,
but it has a too high administrative overhead in my opinion,
and it doesn't really work much better.
They will use up their grace days and
then go over deadline.
If we give them a grace day for all assignments
then we are essentially shifting deadlines in their minds.
After discussions with a few more experienced instructors
I switched to something similar to Suresh's policy for my last course and
it worked quite well.
There was almost no serious complaint.
Here is the policy I used:
1% penalty for every 30min after the deadline.
First, it is easy to implement.
I use an online submission system so it is quite easy to compute and apply these penalties
using time-stamps for latest submissions, it is a simple script.
Second, it is effective way of helping the first two groups.
This policy gives them two extra days after the deadline if they really need.
Most late submissions miss the deadline by a small amount of time.
Being essentially a continuous linear penalty function it makes sure
the penalty is proportional:
a student who goes over the deadline a few minutes doesn't loose too much points.
I give students typically 2 weeks for submitting assignments.
I don't think it makes sense to give more that 2 extra days.
Too many days and too soft penalty
will essentially shift assignment deadlines in their minds and
cause further procrastination.
The hourly lateness penalty creates a sense of urgency that daily penalty would not.
I had around 100 students and they seldom went over a few hours.
I also put deadlines on Friday evenings.
Students who don't like doing assignments
hate to spend their weekend on them.
Student who submit their assignments on time
do not have to worry and spend their weekend working on assignments,
this adds an extra incentive for them to finish it by deadline, or
if not possible with as little lateness as possible.
it also makes sure that the following week
we can focus on our topic
without them worrying about assignments.
To deal with the 3rd group
I don't use my late assignment policy,
I use an special consideration policy.
If a student misses an assignment deadline with a good reason,
e.g. serious illness supported by medial documents,
I apply my special consideration policy to accommodate them
e.g. I may move the points for the assignment to other assignments.