By the US Department Of Education American children must be ready to learn from the first day of school. And of course, preparing children for school is a historic responsibility of parents. It's a loaded word.
Tests are important, especially to school children.
A test may measure a basic skill. It can affect a year's grade. Or, if it measures the ability to learn, it can affect a child's placement in school. So it's important to do well on tests. Besides, the ability to do well on tests can help throughout life in such things as getting a driver's license, trying out for sports, or getting a job.