When I was a grade schooler I either watched the entire Dragon Ball series (including GT) without censoring the blood, Crayon Shin Chan, Ranma 1/2 and other late 80s and 90s series and that was entirely fine. In Japan grade schoolers read Detective Conan for instance (it's really easy to read), same with Doctor Slump and Doraemon. So unless you throw hentai on him, I don't see a problem, you can always check publisher's ratings to choose among them. There are plenty of series he can read, I would recommend slice of life, such as Non Non Biyori, but it's more about letting him choose what he wants to read.
PS: my only concern would be a parent that still reads series like Komi-san.