The onset of puberty for girls typically begins around the age of 12, marked by the development of breasts, the appearance of pubic hair, and the onset of menstruation. At this stage, some girls may not feel ready to wear a bra for various reasons, and parents should respect their child's wishes.

However, by the time a girl reaches around 14 years old, when breast development has largely stabilized, it's essential to introduce bras into their wardrobe. This recommendation stems from the fact that breasts lack bones and muscles, making them susceptible to sagging due to their own weight when standing or sitting. This can lead to uneven distribution of weight within the breast tissue, impeding proper blood circulation and potentially leading to breast issues. Additionally, it can detract from the overall aesthetic of the breasts.

During intense physical activity, the breasts can bounce up and down, causing discomfort. Therefore, wearing a bra can provide necessary support and comfort.

It's also important to note that modern nutrition has led to faster growth and development in children. As such, parents should consider their child's individual development and readiness when deciding when to introduce bras, rather than adhering strictly to age guidelines.