the height of a hoop for a 11 year old should be near 7 ft.
A 12 year old should use a regulation basketball hoop. You do not want your 12 year old to get use to a shorter hoop. A standard hoop is 10 feet high.
its at least ten feat right?
for anyone over the age of 11 the height of the hoop needs to be 3.05 metres high
it matters where u live
If you're just playing around for fun, set the hoop at whatever height you want. When played as a sport though, the hoop is virtually always set at 10 feet. Though some youth leagues for kids under 10 years put the hoop at 8.5 feet, I'd recommend playing or practicing with it at 10 feet, so that you'll learn skills applicable to school basketball, and you won't have to readjust your technique later on.
about 2 metres high