Schools minister Nick Gibb said he had already seen the exam question for 11-year-olds that he got wrong live on air.
Mr Gibb revisited the embarrassing episode as he defended tough tests for 11-year-olds at the Brighton College Education conference.
He said that children, especially those who do not live in homes where books are a part of daily life, would be helped by tough tests in areas including spelling, punctuation and grammar.
Mr Gibb came unstuck earlier this week after failing to answer a Key Stage 2 exam question when he appeared on the World at One radio programme.
He was asked to tell the difference between a preposition and a subordinating conjunction.
He told the delegates: "I looked at the very question I was asked on Radio 4 and discussed it, which is why it was surprising I did not get it right."
In response to criticism that the tests may be too hard, he said: "I do keep challenging and asking 'are these questions too difficult? Is it too demanding?'
"The answer I got from our advisers is that it is not difficult if it is taught. These are 10- and 11-year-olds who absorb information and absorb knowledge. If they are taught, the argument is they can do it and answer those questions."
He said that critics may be people who already write well-constructed grammatically-correct passages.
He said: "Our argument is that if you do not come from a home where your parents speak in a grammatically correct form and if you do not have a home surrounded by books where reading is the daily occurrence, they (those children) need that structural instruction.
"Imagine in a few years' time, we will have a generation of pupils leaving primary school with a firm grasp of grammar, a better grasp of grammar than I have.
"I am very optimistic about our reforms. They are demanding. We are raising expectations.
"We looked around the world to benchmark our curriculum against other countries.
"I am convinced we have produced the right curriculum and the right assessments . We always keep these things under review."