If your English is poor, it's right to come here, because you can communicate in Chinese and English here, and it's easy to ask questions if you don't understand, and you make rapid progress.
But you must take a private exam. Except for the scholarship winners at the beginning of China, Lai and Guo, you should not pass the exam. I went to a language school before I came here, so I don't have to take IELTS.
You can report to school when you get your student ID card. There are not many private ones here, and they are easy to find online. You can visit www.sgchinese.com.
Most importantly, don't trust the intermediary too much.