What is happening here?
At the end of primary school many things matter at once: which school fits, how does it go on after the summer? For math the rule is: Grade 4 adds nothing completely new, much of it is deepened. Secondary school builds on written calculation with all four operations, on a confident handling of measures and on word problems.
Which type of school is recommended is decided by the school under the rules of your region and never by a single math test alone. If in doubt, ask the class teacher.
What helps at home
Have your child explain how they reached an answer, out loud and in their own words. Anyone who can explain a calculation has understood it. Checking after every written calculation and estimating before it are the two habits that pay off most in secondary school.
Puzzling trains exactly what is needed there: trying systematically, checking solutions and not giving up. Magic squares, number riddles and tasks like "How many ways are there?" suit an evening or a car ride. Ten minutes are enough.
What can go wrong
Pressure is the biggest brake. A child who is afraid of mistakes calculates more slowly and makes more of them. Rather say: "That is a good mistake, what can you learn from it?" Anyone who finds a mistake has understood something.
Breaks belong too. If a task does not work out after ten minutes, a break is better than one more try with frustration. Many solutions arrive on a walk. And do not compare your child with others, but with their own level of half a year ago.