Jmo, but 8th graders don’t usually have the life experience to write with the sort of self awareness an app/supp needs. Nor the editing perspective. I’d say even rising 11th graders struggle (including those who say they love to write.) They need time to live life. Get the hs basics first and try not to have this different style interfere with the skill set needed for hs. After that, you extend their range.
Everyone will say reading and more reading sharpens their thinking and observation skills. Imo, get there before you polish. A great writer IRL is usually a great observer first. You can work on that, but keep in mind this is an 8th grade brain. Don’t burn out any affection for writing.