no online drop with overdue balance

we have to many parents dropping online and expecting not to pay overdue balances - either showing them overdue balances on dropign a class so they know it is still to be paid or an error message to pay overdue balances before their drop is complete - the process of an online drop is easy and simple and we like that parents feel like they have control of their account however we are constantly chasing parents after they have dropped to get outstanding fees before we make them inactive or they are enrolled in auto pay the money coming out for overdue balances after they feel their drop is finalised has created some tention