S.H.
5 years old is very common.
My son is 5.75 years old and just lost his first tooth.
My daughter was about that age as well when she lost her first tooth.
My son's Kindergarten Teacher says, it is common.
I also work at my kids' school and everyday, Kindergarten aged kids were SHOWING me their loose tooth or teeth. Or showing me the gaps in their mouth of where they lost their tooth.