The six bubbly Year 1 primary pupils have just spent 40 minutes taking part in games involving adding and subtracting numbers to 10 and counting to 20.
Discipline has been maintained throughout.
It would appear that Dartington primary - a training school - has turned out another two excellent trainees who are confident that they can teach number lines, bases and counting to Year 1.
However, far from being ordinary trainee teachers, Jess and Molly, both aged 10, are fellow pupils.
The class is part of the Devon school's initiative to allow Year 5 and 6 pupils to aim for the school's own primary qualified teacher status (PQTS).
Jess, who got the PQTS last year, said: "It is kind of weird. You are in the world of the teacher. You find out how hard it is to teach lessons."
The initiative was launched last year with two groups of Year 5 pupils.
This year's Year 5 will start next term.
Pupils are taught to observe, plan and ultimately take lessons of fellow pupils in Year 1.
Each pupil takes three or four small groups, such as Sebastian's, and spends other lessons assisting a whole class with the regular teacher.
To gain the award, pupils are assessed against five of the national QTS standards.
Pupils have to demonstrate secure subject knowledge, that they have high expectations of all pupils regardless of background and show concern for children's development as learners.
They should promote the positive values, attitudes and behaviour that are expected from pupils and be able to plan lessons for children's varying abilities and needs.
The scheme was devised by Leah Fraser, the school's training co-ordinator.
She said: "The first thing they asked was how could they keep a class of 20 quiet."
Annie Tempest, the headteacher, believes that the experience benefits all pupils. "The aim is to give all the children a chance to do it. We find their own learning is so much better.
"From teaching, they know there is more than one way to get at information.
We found they are very strong on discipline and good at engaging those who don't put themselves forward in lessons."
The scheme is one of a number of innovations at the school, which has won Department for Education and Skills recognition.
Dartington has joined in a federation with nearby King Edward VI secondary and Bidwell Brook special school. A teacher from each school is spending a term teaching in each of the others to gain ideas and spread good practice.
Jane Richardson, English teacher at King Edward, said: "I am beginning to understand how literacy works across the curriculum in primary. We are looking again at how we can deliver that at secondary level."