Tens of thousands of kids in England are due to start their Sats exams on Monday - but many won't be taking them.
Head teachers in lots of primary schools say children get too stressed out, so they've called them off.
But pupils in some schools will still have to sit them if their head thinks it's best.
Two of the main groups which look after teachers' interests took a vote, and the majority of teachers said they didn't want the Sats to go ahead.
Around 600,000 11-year-olds in England are due to take their Maths and English Sats this week.
Many teachers have voted not to support Sats because they think they are bad for children, teachers and schools.
They believe that Sats cause everyone too much stress, and that schools end up teaching kids how to pass exams, rather than concentrating on helping them learn different subjects.
The headteachers who support the action will ask their teachers not to open any Sats papers, not to check them and not to carry out the tests.
The teachers and pupils will all still be in school on the days the Sats are supposed to take place, but the tests won't happen.
The two teachers' unions which have voted against Sats are called The National Association of Head Teachers (NAHT) and the National Union of Teachers (NUT).