Based on your query, I would recommend MagicSchool AI. This tool offers an "Advanced Proofreading" feature that can identify writing issues in students' assignments and provide constructive feedback. This feature could be used to generate the wrong sentences you're looking for, as it can identify and highlight incorrect or poorly constructed sentences in students' work.

Moreover, MagicSchool AI is designed to be user-friendly with an intuitive interface, making it easy for you to navigate and use the tool effectively. Currently, it's free for teachers, which adds to its appeal. However, please note that the platform plans to switch to a subscription model in the future.