I sincerely hope you both will stop and consider carefully what your parents are telling you. No doubt they have seen other young couples in similar situations, and they know how easy it would be for you to make a mistake.
But I also hope you will stop and consider the consequences of going against your parents' wishes and marrying secretly now. Eventually they will find out what you've done and when they do, what will be their reaction? In all likelihood, it will cause a great deal of mistrust and tension between you and quite possibly a serious break that could take years to heal.
I pray you won't let this happen. The Bible says, "Let us therefore make every effort to do what leads to peace" (Romans 14:19). Sometimes this is hard to do but in the long run, it is the best path. Your parents know that it's very important for you to finish your education, and they know too the dangers of making unwise or hasty decisions.
The most important advice I can give you, however, is to seek God's will for your future. He has promised, "I guide you in the way of wisdom and lead you along straight paths" (Proverbs 4:11). In addition, keep the lines of communication open with your parents. Listen to them and help them listen to you. If it is God's will for you to marry now, trust Him to change their hearts. Remember: They love you, and they want what is best for you.