What is the ruling on money sent to a student studying abroad for his upkeep, but he concealed his repeated failures from his family?

Lying is a reprehensible and forbidden trait. You must repent to Allah for lying and be truthful with your family by informing them of the truth about your academic failure. As for the money, if your family made your success a condition for sending it to you, then it is forbidden for you in case of your failure. If they did not explicitly state this, then informing them of the truth about your failure is more appropriate.