Réponse :
I think that it's smart because he is going to have what he wants even if it's not right. He souldn't talk to the teacher because she would give him a fail instead of a pass.
It was a good idea to don't tell the teacher because she wouldn't understand that he needs this pass. Even if it's not right, may be Liam was not great the day of the exam and this is why he failed. I think Liam is smart because if he weren't, he wouldn't choose to study science at college.
If i had been in this situation i would tell the truth because i'm an honest person but i know that before telling the truth i would think about keep that as a secret.
Voilà j'espère avoir pu t'aider, après ça c'est mon opinion sur ce sujet. Si tu as besoin d'une traduction où quoi que se soit n'hésite pas à me demander . Bonne journée.