It claims the move is due to popular demand and that, after years of antagonism, teachers are now accepting the testing regime.
A pilot scheme of optional tests for nine-year-olds took place last summer and now the Qualifications and Curriculum Authority is producing similar tests for eight and 10-year-olds. All five-year-olds will be given "baseline" tests from next September.
"There is clear evidence that teachers find the tests useful and that is a big turn-round from only a few years ago," said Dr Nicholas Tate, QCA chief executive.
"That indicates a big cultural shift. We are piloting tests at ages eight and 10 this year as a result of demand from teachers who want to be able to measure their progress towards the Government's targets."
But the teaching unions, currently campaigning against excessive workload, warned against assuming that teachers backed yet more tests. Doug McAvoy, general secretary of the National Union of Teachers, said the QCA should survey individual teachers.
While last summer's compulsory tests for seven, 11 and 14-year-olds demonstrated improvements on previous years, the new optional tests for nine-year-olds were less encouraging.
They showed a worrying drop from the standards reached by seven-year-olds with nearly half the sample of nine-year-olds failing to make the progress expected of them - threatening the achievement of national targets at age 11. According to the QCA, the pressure of key stage 2 tests has distracted attention from this group.
The biggest worry was mathematics where only 55 per cent reached the target of level 3.
The QCA also remains anxious about lack of progress in maths and science at key stage 3 (11 to 14-year-olds). Chris Woodhead, the chief inspector of schools, has already voiced concern that secondary schools might be putting their weakest teachers in this area.
The authority promised to tighten up security for next year's tests after complaints that schools were cheating. A survey of heads showed that three-quarters thought the arrangments were too weak.
In future papers will be sealed until an hour before use and schools will be subject to spot checks.