What time does baby go to bed?

I usually tuck my kids to sleep around 10pm but as for my 5 months old baby, he is usually asleep by 8pm but will wake up again ard 10pm for milk together with his sister and brothers. Sometimes, my girl who is 8 years old, Primary 2, in the morning session, she may feel more tired earlier and request to sleep like 8.30-9pm. She has to wake up around 6am in the morning to prepare for school. All my other 3 boys are early riser irregardless what time they sleep. Usually once the bedroom lights are on, they will automatically be awake too. My kids are going childcare centre and they have their routine time to sleep there, therefore, I can't make them sleep too early else it will be worst cos they won't want to sleep and you will have to be up with them till at least 11 or 12mn.