A father and his 14 year old son were at a drug store when
the son noticed a pack of condoms on the shelf.  "Hey Dad,
what are these?"  "Well son, those are used for safe sex"

The son picks up the package and asks, "why are there 3 in
here?"  The father replies, "these are for High School
students - one for Friday, one for Saturday and one for
Sunday".

Then the son picks up a package of 6 and asks why there are
six in there.  The dad answers, "those are for college
students - two for Friday, two for Saturday and two for
Sunday".

Finally the son sees a package of 12 and wants to know why
there are twelve in the box.  His dad simply says, "that is
for married men, one for January, one February...."