Show the cards one by one, and mark them with an OK if they can read them correctly.
If they struggle a little, mark a △.
If they can't read them at all, mark an X.
Record the time it takes them to read them all, and also record the time it takes them to read them all.
Show your child the katakana they couldn't read and teach them how to read them.
Show your child the cards they couldn't read again to see if they can read them.

Apparently, doing this every day will help them become fluent in reading katakana. Apparently, once a day is enough. Doing it too many times will make them bored. Even if your child wants to try again, have them do it the next day.
That's what the teacher at school told me.
Since we actually use real cards, the school provided the cards.

We created this app for reasons such as using real cards being inconvenient to carry around, tedious to record, making it difficult to measure time, and confusing the punched holes and the ゜ on the cards.

Please feel free to use it.

The hiragana version is called "Hiragana Reading."
https://play.google.com/store/apps/details?id=jp.takesignal.hiraganayomi&hl=ja