I’d imagine he meant to say 28…..and 27 is pretty fast for a 6th grader…..I certainly wouldn’t have moved you to 800m at that age.
Welcome to the board. In my heavily biased opinion this is the best track site on the web :D. There is probably too much information on this site for you to ever get through. If you don’t find what you’re looking for on the messageboard, there are over 200 articles in the main part of the site, many of which are devoted to sprinting and general conditioning.
As for you personal request, many people on the messageboard have asked for the very same thing you have (speed + endurance). In general, it’s best to focus on one rather than both at the same time as you won”t get optimal gains that way. For starters, I’d suggest looking through some of the training journals…..400stud and dagovernor both have nice training journal threads dedicated to 400m training. If you still find that this isn’t what you’re looking for come back and ask another question.