Most children start getting their permanent teeth in between ages 6 and 7 years old.
Some children may start losing their baby teeth as early as 4 and 5 years old and then by 6 or 7 years of age and sometimes as late as age 8 the child's permanent teeth should be fully in.
I started losing baby teeth around 5 and 6 years old and then after 8 years old my permanent teeth were in and I had lost all the baby teeth.
All the baby teeth should become loose and fall out on their own without needing to see a dentist and sometimes the kid can even pull the loose tooth out by themselves.
All kids are different but by age 8 and even sometimes 9 years old then the child should have all permanent teeth in and all the baby teeth should be lost.