"They're arguing about safety regs instead of last night's football," he says. "It's amazing."
But then he and his fellow lecturer, Stuart Raine, did help to shape the materials in brainstorming sessions hosted by the Department for Education and Skills.
Both men are trained carpenters and joiners with experience in industry.
They are fired with enthusiasm about new ways to spread the safety message.
The Standards Unit's new materials for construction - one of the four curriculum areas being rapidly developed - focus on the concept of the "safe learner". With three fatalities a week in the building industry, this is, quite literally, a matter of life and death.
The team behind the new materials found the teaching of theory was too often dull and unimaginative. They believe that games and simulation, which encourage learners to enact rather than simply listen, stand a far better chance of making an impact.
Messrs Liston and Raine have embraced the new materials, and so have the wide range of students at Shrewsbury, from 14 to16-year-olds taking NVQs to returning adults.
"We've now got something to work with that can make things better for our students," says Mr Raine. "These materials lead to a new style of delivery and ways to engage and involve them." Students as young as 14 are now adept at carrying out risk assessments, he says.
Different teaching methods have already improved the department's inspection rating. Graded last summer at level 4, the lowest rung, it was given the top grade in an interim inspection in December.
"The inspector said that if he could bottle the enthusiasm he found here, he'd take it to other colleges," says Mr Liston.
The new ideas have had an immediate impact. For example, Safety Signs, a board game in which learners have to identify site warnings correctly, is also available in a computer-based drop-and-drag version. The game goes down well in group work and tends to prompt lively discussion.
"It's good for reinforcement and fast learning - and can be used with all learners," says Mr Raine.
There is also a card game about accident prevention. This has likewise provoked useful discussion and deepened students' understanding of the Health and Safety at Work Act.
Shrewsbury is one of 40 pilots and its reaction is typical.
In the third curriculum test bed area, science, there was a great uphill struggle. "Science teaching is dull", was the damning verdict from a parliamentary select committee. Two years ago, 19 per cent of lessons in science and maths were found to be unsatisfactory - that's nearly twice the average for all learning.
But the new materials being piloted are already helping to change teaching styles, says Michael Kalvis, the Standards Unit's project manager for science. His team is focusing on particular areas, such as biological molecules and enthalpy (the chemistry of heat), both of which have proved to be difficult to grasp and to be building blocks to later learning. In effect, the learning process itself is now under the microscope.
Feedback from teachers and learners involved has been encouraging, he says.
"The transition from being a talking teacher to a listening teacher can be a difficult move, and even experienced teachers can find it hard to change their approach," he explains.
Business studies, the fourth test bed curriculum area, attracts so many learners from ethnic minority groups and disadvantaged backgrounds, that boosting it will help promote greater social inclusion. At least that's the theory. New materials that radically overhaul phase 1 of the business studies framework were drafted last summer, and are now being piloted with 31 providers.
Like materials in all four test bed areas, they will available nationwide from September.