kosmik Economics is a question of voluntary exchange.
If the community, via taxes collected by the State, pays for a service there are two ways the community can recoup that cost.
One is the on-going benefit that that the community gains from the expenditure, public roads come to mind here and education is another example, but only if the education system produces people who are productive.
The other is a more direct demand on the individual beneficiaries of a service. Toll roads are an example of this. Limited community service for individuals who have benefited from an education is another example.
If an individual beneficiary of an education wants to leave the country then the only way that the community is going to recoup the cost is by community service.