Salah for little brother

:sl:

I have a nine year old brother and Alhamdolillah prays all his salah with a bit of encouragement, but now esha time is becoming later and fajr earlier, so he ends up going to bed around 11pm after praying esha and my wants him in bed right after maghrib around 9pm and even the latest he can pray fajr is around 4.45am so my mum doesn't let me wake him up.

So I wanted to know if its ok if my mum stops him praying these salah at this age, because he doesn't get enough sleep and wakes up late for school?

:w: