dealing with distractions

Even though we have just BARELY started our school
year, the distractions are already present...loudly present.

I'm not sure there is a simple solution to this problem...
because some distractions are necessary
(Dr. appts., trip to the post office, etc.),
then some are just so tempting to welcome with open arms,
aka, a call from a friend.

In the past, I've tried to keep our focus but never
really made a big deal of getting off track
with our school work,
but this year is very different because both of my
students (well, the two I have at the moment) are
high schoolers and they really must work hard to get
all their subjects completed by the end of the year
in order to have a full and impressive transcript.
And I DO NOT want to work into the summer.

So, does anyone have a great solution to this?
Do any of you do 4-day weeks in order to
put those errands and Dr.'s appointments on the
5th day?

Do some of you simply require your students
to do "homework" in the evenings?
I really try to avoid that but I think it's going to happen for us this year.

Your thoughts?