I assume he is on legal aid.
The only way you can apply for child support is to go to the child support agency. It is not done through court. The court only deals with the time the children seen with the parents and where they live.
Here is the link
The law only requires him to pay what he is assessed to pay and no more.
If you want the children to go to private schools and he does not want to pay extra he is not required to. He only has tp pay what he is assed to pay.
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