The Student is the main protagonist of the Japanese Commercial Yes Milk! (はいミルク)
The Student is having lunch with his friend then he sees that he’s been drinking a lot milk he asks him why, and he says that it improves “concentration”. the student starts having an imagination if he had concentration where in class he is dodging a bunch of chalk thrown by his teacher and has teacher turn into a giant chalk then stops her.
then after the imagination he begins to take his friend’s advice and drink lots of milk.