I suppose it depends. Both our kids could do it before they were out of PreK (well before 5th birthdays). But, they didn't start out tying them the "standard" way, they did some double loop tie thing my husband taught them. Then I taught them standard after that. And it wasn't like they were fast at it right away, either. It was still faster for me to do it than for our daughter when she was 4 or 5.
But we made an effort to have them do things for themselves, and they wanted to do it. If we had always done it for them and hadn't spent any time on it at all, then I would expect it to be somewhat "normal" for them not to know how at age 6. If, as we did, we had made an effort and they still hadn't figure out how to accomplish it in 2 years, then I'd consult with the pediatrician. Perhaps some fine motor skills issues are flying below the radar and need to be addressed.
I will say that we went through phases with both kids where we used bungee laced shoes or velcro strapped ones. It was faster, but we bought those particular shoes more because they fit than anything else. :)
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Wow, just read the other responses. Maybe it's more normal than I realized. I know my son's K4 teacher said "anything they *can* do on their own, they will be expected to do on their own... anything else I'll be glad to help with." He could tie his shoes, put on his jackets, and write his name without assistance. So he was expected to. I suppose other kids received assistance with those things.
Daughter always tried to keep up with older brother.
I can definitely see how lack of opportunity would slow the process down. So many shoes don't have actual laces these days. Our kids' did, for the most part, except for a pair or two here or there.
Does your child have laced shoes? Has he always had laced shoes? Or has he had a lot of velcro ones?