In general, the jaws develop most during the pubertal growth spurt. This means that orthodontic treatment progresses most quickly and effectively if it starts shortly before the child reaches their teens. Parents can tell when this period is approaching from the visible increase in the child's height and the appearance of secondary sexual characteristics – the voice breaking in boys and periods starting in girls. After the peak of puberty, we can still hope for some jaw growth, but it decreases.
This answer is for general information. Your own case needs an examination by an orthodontist.