Yes, you certainly can be a Christian and a scientist. In fact, some of the most brilliant scientists in history–men like Pascal and Newton–were strong believers in God. It has also been my privilege over the years to know many outstanding scientists who were also committed Christians.
I would even contend that being a Christian will make you a better scientist. Christians realize that this is God’s world; He created it, and everywhere you look you will see His footprints (so to speak). The Psalmist put it this way: “The heavens declare the glory of God; the skies proclaim the work of his hands” (Psalm 19:1). When a scientist discovers something “new”, he is really only uncovering something old–something God already did.
As a Christian, you also will want to be the best scientist you can possibly be, because God gives us our abilities, and He wants us to do our best. The Bible says, “Whatever you do, work at it with all your heart, as working for the Lord, not for men” (Colossians 3:23).
I’m sorry your teacher sometimes makes fun of Christians, but don’t let him discourage you or turn you away from Christ. The most important decision you will ever make is to follow Jesus, and if you have not done so, I pray you will ask Him into your heart today. Then ask Him to guide you in the future–and He will.