The anxiety on Paul's face when he is asked to read aloud shows how he hates every second. Lucy, even before she starts to speak, is blinking her eyes furiously.
For both, getting words out is agony and, like the thousands of other children in Scotland who stammer, they would do almost anything to avoid talking in class, including saying "Here".
"Registration is a particularly hard process for children who stammer and many try to avoid it by being late," says Norbert Lieckfeldt, chief executive of the British Stammering Association, which is launching a free support CD-Rom for schools this month.
"They will often develop such tactics to hide their problem. But there are ways teachers can make it more bearable for these pupils. This isn't rocket science and the strategies are not onerous."
Teachers may recognise the tactics. They include looking away or closing their eyes to avoid seeing the reactions in others as they try to speak.
They may cough, blush, drop a book and even pretend not to hear. Talking around the problem so the meaning is hard to discern, or using monosyllabic answers and filler words such as "y'know", "right" and "kind of" can all hint at stammers. So can silly or challenging behaviour.
While teachers may be familiar with this behaviour, recognising that it could mask a speech problem is difficult, especially in secondary schools, where contact is limited. Unwittingly, they may be compounding the problems stammerers face by rushing or reprimanding them.
"If anything, teachers are guilty of ignorance of how to deal with a child that stammers," says Stuart Maxwell, headteacher of Eastwood High, which together with Crookfur Primary, both in Newton Mearns, East Renfrewshire, played host to the BSA's film crew for the CD-Rom.
"The CD-Rom is an awareness-raising exercise, but what makes it so strong is the presence of real children who stammer, explaining how it feels," he says.
Five per cent of pre-school children in Scotland stammer. The percentage drops as children get older but by secondary school age one in 80 still agonise over their words. The majority are boys.
No one quite knows why people stammer. However, the effect it can have on a child's development is clear. At school, they can suffer embarrassment, frustration, guilt and lack of confidence, as well as bullying and teasing.
Early intervention with a pre-school child as speech develops has proven effective, but for those who continue to stammer past the age of 5, it can be a serious affliction. Speech can be littered with stoppages, hesitations, repetitive or prolonged sounds and silences caused by airflow blockages.
"Stammering is not simply a speech difficulty; it is a serious communication problem," says Mr Lieckfeldt. "It can undermine confidence and self-esteem, affect interaction with other people and damage education and employment prospects."
Funding from the Scottish Executive has enabled the BSA to produce the CD-Rom, which features Paul and Lucy, among other children who stammer.
Three versions have been produced, covering primary, secondary and English oral work from S1-S4. All Scottish schools will receive a free, relevant copy before half-term.
The BSA hopes that using it in group training or individually will help teachers to recognise and deal with speech and language problems better.
"It includes simple strategies, which can be implemented in the classroom without extensive training," says Jan Anderson, the BSA Scotland development manager, who hopes to offer some support training. "Children should be encouraged to talk through their stammer, because this helps them in the long term, but it needs to be done sensitively and with encouragement."
One recommendation is to allow a child who stammers to read out aloud with another child, rather than on his or her own. This can encourage fluency and overcome embarrassment.
Another is being more flexible in registration, accepting a raised hand, rather than a "Here, Miss", from anyone in the class, not just those with a stammer. If the start of a lesson is easy to get through, the rest may be less of an ordeal and pupils such as Paul and Lucy may find it easier to cope.
* Aim to build self-esteem so the pupil manages hisher speaking with confidence, even when stammering severely.
* Give time to pupils to finish and do not interrupt or finish off words.
* Listen attentively and echo back some content, so the pupil feels that what heshe has said is more important than how it was said.
* Maintain normal eye contact and do not show impatience (such as frequent nodding, getting on some task or signalling irritation through tense body language).
* Slow your own speech with natural pauses, signalling that there is no need to rush.
* Talk regularly with the pupil about what strategies are helpful.
* Encourage the pupil to participate in all oral activities.