Desks shake and pupils cower as thunderous footsteps approach. Finally, the creature enters the room and fixes her victims with a hideous glare. Miss Rancid, the supply teacher, has arrived.

The scene is from the children’s cartoon Horrid Henry but it channels the ominous terror of Jurassic Park.

English football manager Tim Sherwood tapped into a related stereotype earlier this year. He complained that he could not command respect from his Tottenham Hotspur players - because they viewed him like a supply teacher.

These are deep-rooted preconceptions: the supply teacher as unhinged sadist or weak stand-in, not good enough for a “proper” job. Very often, they are a million miles from the truth.

In my schooldays, supply teachers frequently brought freshness, vim and a willingness to depart from the rote-learning script (this was more than 20 years ago). Liberated from the trudge towards exam results, they seemed more inclined than our usual teachers to get us talking and thinking.

Sadly, the stereotypes trump reality in popular perception, and teachers who rely on supply work often feel unappreciated and misunderstood. Morale hit a new low in 2011 when supply teachers were hammered in that year’s national pay deal.

They would have to work for five consecutive days to get the full rate of pay, otherwise their salary was effectively halved. Suggestions soon followed that schools were taking on supply staff for short periods only, below the five-day threshold, then hiring them again later so that the higher rate of pay never kicked in.

There was outcry. Members threatened to leave Scotland’s largest teaching union, the EIS, for not doing more to secure a fair deal for supply teachers.

Feelings are less raw now, and EIS members voted earlier this year to reduce the pay threshold to two days. Resentment lingers, however, and many supply teachers have disappeared from schools, deciding that the work just isn’t worth it any more.

This summer, TESS reported on the dramatic year-on-year decrease in supply hours (“Cuts in cover expose `significant problem’ ”, 1 August). Among the councils that responded to a Freedom of Information request from the Scottish Liberal Democrats, supply teaching hours had fallen by 16 per cent.

Today, our own survey shows that the vast majority of councils are still struggling to recruit supply teachers - most have fewer on their registers than last year.

When TESS reported this issue 18 months ago (“Union moves to combat shortage of male teachers”, 17 May 2013), supply staff were already talking about being “totally swamped” with phone calls from schools looking for stand-in staff. “I feel like I’m the only one on the [supply] list,” said one.

Now his services are even more in demand. If, of course, he still works as a teacher.

henry.hepburn@tesglobal.com