Fluent American readers are likely to think "practise" is a typo. It's not even one of the commonly-known British/American spelling differences (like "color"/"colour"). Unless you know your audience is likely to be more familiar with British spelling, I'd avoid "practise."
They're not very smart then: most non-native people know there are several big mainstream ways to spell English, and we learn that on top of our own languages.
Couldn't American schools teach English the same way, like, that there are no single proper way ?
