I'm not sure if this counts as a "comic", but it's certainly a story illustrated with sequential images - and it's a story I made in elementary school. I think it was in first or second grade?
I was seven or eight years old, and we were given an assignment by the teacher to help us practise our writing skills - we got a blank notebook where half of each page was a blank white space, and half of every page was lined, and told to make up a story.
I made up a story about two troll boys who lived in a cave together - one who was very tall and had a toadstool on his giant nose, and one who was tiny and looked like an ambulatory shrub - and who went on various adventures. The one I remember most clearly was when they found a baby dragon and took care of it, before letting it go free because you shouldn't turn wild animals into pets just for fun.
Most kids filled maybe one notebook in an entire year. I filled seven notebooks with my animal-protection-themed bromance, and the teacher actually had to tell me to please stop writing, Anna, this is math class.
I drew a new version of the main characters quite recently, actually. If I'd drawn the story last year, they would have looked like this!:
