The school, in Ilford, operates a no-hands-up policy to ensure that every pupil gets a chance to contribute, rather than just the keenest.
It is one of the ways the school, in the north-east London borough of Redbridge, tries to personalise education through "assessment for learning", an approach pioneered by academics at King's college, London.
Teachers also put comments and not grades on pupils' work, although they continue to keep their own records of marks. Staff only discuss grades in one-on-one interviews with pupils.
Corinne Francheschi, deputy head, said: "When you give a grade the student's ego gets in the way and they are blinded to where they are at in their learning."
She led a team of eight teachers who tested the techniques with their classes before spreading the practice to other staff. Their findings have fed into reports by the Economic and Social Research Council.
Valentines has also been working on other key components of personalised education including creating partnerships with other schools and providing a broader curriculum.
The school has invited staff from John Laing, the building company, to run a formal vocational construction course each week, giving pupils a chance to master such skills as plastering and bricklaying.
Valentines also oversees the construction course in five more of Redbridge's secondary schools and a special school.