In a briefing paper for staff that was leaked to a local newspaper, the head lists high levels of juvenile crime, high numbers of single-parent families, pupils with jobs and lack of parental support.
"Although drug taking is not a major issue in or around the school itself (as far as we know), there are major issues facing pupils in the evening. A sizeable number are involved in taking cannabis and some of these, together with many others, have parents who are heavily involved in the drug scene - either as users or suppliers.
"The ability of such pupils to study and work is almost impossible.
Cannabis, while only very mildly addictive, does have the effect of giving the child a laissez-faire attitude both in the evening and the following day."
Mr Barker, whose school won the 2002 Scottish Schools Ethos Network Award, continues: "One of the main threats, however, to a child is alcohol abuse.
This is even more common than drug taking and is the biggest single form of abuse that exists. There is a need to control the alcohol supplied to our pupils. Easy to say, but difficult to do.
"If an inroad to any of this can be made, then attainment will rise."