Children should not be trained for tests at the expense of developing "essential" skills such as reading, writing and grammar.
Former headteacher Kit Messenger, speaking on ITV's Good Morning Britain, said she does not favour test preparation "to the sacrifice of skills that are absolutely essential for children's futures".
Although she advocates rigorous maths and writing teaching, Ms Messenger places more emphasis on developing workplace skills such as resilience and interpersonal ability.
Ms Messenger added exams "do not necessarily tell you where children are", and that "there is not the time within the curriculum" to prepare children for tests".
"If you look at the quantity that is required for teachers to teach in order for children to be successful in the papers now - it is to the sacrifice of everything else," she said.
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Parents will be taking their children out of school tomorrow in an unprecedented "strike" against compulsory exams for six-year-olds.