They no longer have to deal with weeping parents upset at their child's performance, and have more control over the syllabus. Pupils are also more interested in the subject.
But their new-found freedoms in a test-free classroom have come at a price - heavy workload as a result of "onerous" and inconsistent assessment procedures.
The Wellcome Trust, the world's largest medical research charity, studied the effects of national testing in science at key stage 2 in England and Wales.
It revealed that most teachers in Wales believe abolishing Sats, the tests at all key stages which ended last January, has been a "positive and welcome" change for the nation.
Some 62 per cent of Welsh headteachers said standards had improved as a result, with only 17 per cent disagreeing.
But in England, pupils are being "turned off science" by months of test preparation.
In Wales, teachers believe assessment gives a better indication of science ability in the age group than the old testing regime.
But there is also discontent among teachers, with many of the 300 questioned calling for clearer guidance from the Assembly government on assessment and more classroom support.
"A number of Y6 teachers and science co-ordinators commented on a sharp increase in teachers' workload as a direct result of the changes in assessment procedures and practice," says the report.