Your trip sounds fantastic! But, I agree that you should avoid staying at Grand Central Hotel. A better hotel in the same price range is Value Hotel Thomson (stay in top room with a window): https://plus.google.com/105132834002001776545/about?gl=nl&hl=en. Metro is 10 minute walk from hotel, which should be fine. Where is your school located.
I think you will enjoy Singapore. The education level is excellent and it will give you some good training.