Walaikumasalaam,
Please have a read of the below advise:
Praise be to Allaah. A person is not considered to be accountable until after reaching puberty. Before puberty he or she is not accountable, because the Prophet (peace and blessings of Allaah be upon him) said:
“The Pen has been lifted from three: from the child until he reaches puberty, from the sleeper until he wakes up, and from the one who has lost his mind until he recovers.” (Narrated by Abu Dawood, 4402).
Based on this, then a girl has to put on complete hijab when she reaches puberty. There are three signs of puberty that males and females have in common: 1 – Nocturnal emissions (wet dreams)2 – Growth of coarse hairs around the private parts3 – Reaching the age of fifteen
If you wish to read more please visit:
https://islamqa.info/en/20475
Please ensure the above site follows your school of thought/madhab.
Jazahka Allah.