How to handle a teenage boy

Hello mga ka mumshies! Hingi lang po sana ng advise kung na experience nyo na ito. May teenage boy po ako, currently at grade 8th. I recently found out he's been having a chat with a teenage girl (who has a bf), whom he expressed interest with, however he got rejected. My initial reaction was that I felt betrayed coz we had an agreement that he is to focus on studies and to make having a gf least of his.priorities. that's all I asked of him since I'm a sjngle mom and he witnesses how difficult it is for us. However, he is keeping stuff like this as a secret. Thank you po sa makakapag bahagi ng advise.