LO 3 months not drinking milk in IFC

this is the 2nd time the IFC teacher feedback to us that our LO is not drinking his milk properly in school. previously no issues in school and we did not change his milk or make any adjustment to his feeding. We even change the milk teat to medium flow few days ago. Just now, he drank 20ml for 2 feeding times at 3h interval. Afterwards he drank the full 120ml. So I don't know what is the issue and feeling a little lost and down that my LO is not having a proper milk intake twice. Please advise.