My child is weak in maths - what should I do first?
Before deciding she is ‘bad at maths’, find out which specific topic actually broke, because maths is built in layers and almost nobody is weak at all of it evenly. Take whatever she is stuck on right now - long division, fractions, percentages, algebra - and test her, calmly and without any pressure, on the topic that sits directly underneath it. A child stuck on long division is usually shaky on multiplication tables, not on division itself. A child stuck on percentages is usually shaky on fractions and decimals, not on percentages as a new idea. A child stuck on algebra is usually shaky on basic arithmetic fluency, not on the concept of a variable.
This matters because it changes what ‘more practice’ should even mean. Ten more long division worksheets will not help a child whose actual problem is that she has to count on her fingers to work out 7 × 8 - she will make the same tables-based errors ten more times, more slowly, and conclude she is bad at maths in general rather than realising she is missing one specific, fixable thing. The practice needs to happen one layer down, at the actual broken link, before it moves back up to where the trouble is showing up in her homework.
The rest of this post is built around finding that link. There is a class-by-class table further down showing what typically depends on what, a short diagnostic for telling a genuine skill gap apart from maths anxiety or a comprehension problem in word problems, and a section for parents who are not confident in maths themselves and worry that matters. If you would rather have someone else do this diagnosis properly - a trained teacher, listening to how she actually works through a problem rather than just marking the answer wrong - our Maths tuition and online tuition classes exist for exactly this: finding the one topic underneath the one she is stuck on, and fixing that first.