Which subject is most important to teach? Well, Math you will use everyday of your life. Language / Speech you will need to make a wonderful impression wouldn't you say? What about Bible / religion? I would say Bible is the most important. The Lord has laid out a plan for each of us and gave us a guide map to go through life. We need to know and use it.
You can have a 4.0 gpa, top of your class. But if you don't know God and his word, it means nothing. God isn't going to look at your report cards, gpa's, thesis' or even count up all your good deeds! All he will look for is your name in the Lamb's Book of Life.
Does that mean we shouldn't care about our grades or work ethic?
No; the Bible say in Colossians 3:23 -
'Whatever you do, work at it with all your heart, as though you were working for the Lord and not for people.'
So you should always do the best that you can and make it pleasing to him. He sees all. Yes, we should do good deeds, do the best in all we do, but that won't get you eternal life. We must know and have a personal relationship with our Lord, Jesus Christ, study his word and you must know the ABC's.
A= admit that you are a sinner
B= believe that the Lord sent his only son, Jesus Christ, to die on the cross for our sins.
C= confess that you are a sinner and ask the Lord for forgiveness and into your life.
ABC's. Cannot get anymore simple that that. :)