İkisi de "Okula gittin." demek oluyor.
"You did go to school." derseniz vurgulamış oluyorsunuz. Mesela:
"I did not go to school. I had something else to do."
"You did go to school. I saw you."
"You went to school." derseniz sıradan bir cümle oluyor. Örneğin:
"You went to school and then took the bus."