Karen Pannett, Montalbo's maths co-ordinator, offers the armbands to pupils while explaining that they offer invincibility against the numerical enemy.
"She says it gives them maths powers," said Gillian Bainbridge, Montalbo's headteacher. "She says, 'Now you're invincible, these numbers can't get you'. A lot of children have a real numbers phobia. We sell the club to them as a way to make them faster and more confident."
The half-hour classes use games and problems to boost children's confidence.
The school also runs more subtle catch-up sessions as part of mainstream lessons. During group-work, less able pupils form a small group who are overseen by a learning support assistant.
Ms Pannett is sceptical about the Government's plan, as recommended by the Williams Review, to offer pound;8,000 incentives to encourage primary teachers to undergo specialist maths training.
"I can see the advantage, if you wanted to brush up on your knowledge," she said. "But you don't need to be a maths specialist - not at primary. Delivery is more important than training."
In fact, she believes it is often helpful for catch-up classes to be taught by someone who is not a specialist.
"Sometimes it's an advantage to have struggled a little bit yourself," she said. "You understand other people's problems.
"We teach within a jokey setting, so that children enjoy what they're doing. I want them to love maths, to see the value of numbers and to give them enjoyment and confidence.
"Those types of things come from instinct in the teacher. To some extent, I don't think you can teach them."