"Aqueles que praticam mais aprendem mais."

Translation: Those who practice more learn more.

[msbraz]

A more direct translation of 'those that practice more learn more' seems fine to me as well. I'm a native english speaker, and I wouldn't find anything unusual if someone said that phrase.

[lobishomem]

Agreed. Marked me wrong for the same thing. Really "Who" is "Quem" not "Que". Another flaw in duolingo.

[AimeLesLangues]

I reported "that" instead of "who" being considered incorrect. Maybe they'll start to accept it.

[philippontheroad]

Thanks. They accept it, now.