IT IS 3pm by the time Bill Flynn finishes his eight-hour teaching job at the Salemwood school in Malden, a residential suburb of Boston. But his working day has only just begun.

Mr Flynn heads off to serve as a referee for a local youth hockey league, then drives to a third job at a company that installs security fences.

The reason that the 43-year-old Mr Flynn holds down two other positions in addition to working at the school is simple. As he explained during a rare break: teaching doesn’t pay enough for a man who has a wife and four children to support.

“Way back when I was 20 years old, I thought I was getting into a noble profession; I still do,” said Mr Flynn, with more than a little bitterness as his students work behind him in his science class. “But we’re getting kicked down by society, including financially.”

Like Mr Flynn, an increasing number of American teachers are moonlighting to supplement their salaries, which continue to lag behind those of other occupations.

Teachers’ relative standard of living has fallen to its lowest point in 40 years, according to the American Federation of Teachers, one of the nation’s two main teachers’ unions.

Th average teacher salary in the United States is about $39,000 (pound;25,000), less than what is paid to a New York City rubbish collector. By comparison, computer programmers make $63,000, engineers $64,000, and attorneys $72,000.

Mr Flynn, who has a master’s degree, earns roughly 25 per cent more than the national average for teachers, and his work as a referee and six-day-a-week fence contractor supplement that salary by about another 80 per cent. Yet his brother, a former teacher now in the computer industry, makes twice as much.

The other major union, the National Education Association (NEA), reports that 35 per cent of teachers now hold second jobs within their school systems as coaches, tutors or advisers to student organisations, and 13 per cent work outside their schools.

Many of the large numbers of young people now entering the occupation at low starting salaries are also taking second jobs. New teachers earn an average of less than $26,000.

“In the past four years, there has been an enormous influx into the profession, and I wouldn’t be surprised if a lot of them were working outside their schools to supplement that starting salary,” said NEA spokesman Steve Wollmer.