Invest in your writing skills - the time and efforts are more than worthwhile for the reward of becoming an effective communicator. After all, the power of the pen (or keyboard, in this case) truly is mightier than the sword.

Additionally, the collaborative capabilities of online learning environments introduce students to peer editing and review. Students can work asynchronously, providing comments and suggestions to each other’s articles, stories, or content, fostering a sense of community, enhancing their critical thinking and ultimately improving their writing.

In conclusion, online learning for middle school writing opens numerous avenues for learners to unlock their potential and grow towards becoming more skilled and confident writers. While it might require some getting used to for both students and educators, the benefits it offers in the long term for bettering writing skills are indeed substantial and promising.

Once the structure basics are ingrained, children should be guided about argument development. Explain to them how to substantiate their ideas with relevant examples and facts. The ability to present evidence effectively to support their central idea is the heart of good essay writing. It would be beneficial to teach them citation and referencing if they're using external sources.

In conclusion, teaching essay writing to kids might take time and effort, but the skills they gain would serve them well in their academic pursuits and beyond. Remember, it's about making the process enjoyable, fostering creativity, and helping children express their thoughts elovably and convincingly.

Next, instilling the importance of structure is vital. Explain the typical structure of an essay, which includes introduction, body, and conclusion. Make it clear that each paragraph in the body should cover separate ideas related to the central argument. The concepts of topic sentences, supporting details, and concluding sentences should be explained.

However, challenges exist in the online learning approach that parents and educators need to address effectively. These include ensuring students stay motivated, dealing with technical glitches, maintaining online etiquette, and preventing online distractions. Care should be taken to ensure that students have the necessary support and resources to make the most out of online learning.

However, while the benefits of online learning are compelling, it’s not without challenges. It demands self-discipline, effective time management, and proper technical setup. Some students may miss the social interactions with peers and teachers. However, many platforms have cultivated interactive virtual environments, such as chat rooms, discussion boards, and virtual classrooms, to foster a sense of community.

Editing and revising are also integral parts of essay writing. After the initial draft, children should refine the work, looking for mistakes or opportunities to improve. Here, they should focus on the structure, language, grammar, and content. Reinforce the idea that revisions don't mean their work is imperfect, but it's a process that all good writers undergo.

Online learning also advances personalized learning, allowing students to tailor their education to their individual need. Lessons can be adapted to suit one's learning style, whether they are a visual learner, audio learner, or read-write learner, which typically leads to more effective learning. The flexibility of online learning also allows regular revision and practice, both crucial for improving writing skills.

Teaching them techniques like 'Show, not Tell', where they demonstrate an idea through descriptive language instead of simply stating it, can also improve their writing. Encourage kids to use a rich vocabulary and a variety of sentence structures to make their essays engaging.

One remarkable advancement is the intricacy of the prompts. Previously, prompts used to be simple and straightforward, requiring minimal critical thinking. They are now developed to be more complex, requiring the students to think deeper and wider. The issues addressed are not only school-based, but also cover wider societal and global matters. For instance, prompts asking students to defend their position on climate change, artificial intelligence, homeschooling etc., require more advanced research, and the ability to present coherent and persuasive arguments.

Moreover, the approach of delivering these persuasive writing prompts has also remarkably improved. Previous methods largely focused on text-based prompts. Nonetheless, the current advancement displays a multi-modal approach, integrating visual and audio aids alongside text-based prompts. Educators now use images, videos, and podcasts to provide context and background information to a topic, thereby adding an engaging layer to the prompts. This enhances students’ creativity and comprehensive understanding of the subject matter.

Thirdly, reading extensively is a guaranteed ticket to enhancing both writing mechanics and style. By reading diverse content, one can explore various writing styles and understand the application of writing mechanics in different contexts. Books on writing, such as 'On Writing Well' by William Zinsser and 'The Elements of Style' by Strunk and White provide foundational knowledge about crafting well-written content.