I have taught for many schools, and agencies, and this one covers all the reasons you'll find online of things to look out for.
I have been teaching ESL in Asia for a long time and ChinaESL is the worst deal a person can possibly get into. Their contract doesn't give you anything. No health insurance, no bonus, no protection, nothing.
They will hook you up with questionable schools, and charge them a third of what they are paying you to keep for themselves on a monthly basis. Try to quit? You'll find yourself either unable or be facing penalties or early dismissal and there's nothing you can do about it.
Everybody loses except them on their contracts. They can end up making more money than you and there's nothing you can do but bend over and take it.
Do NOT hire this agent, Seek jobs that deal directly with the school and do not trust in the job that they are offering you. It likely will not happen and instead you will find yourself paying for an illegally obtained work visa and be placed with a bad school, and penalties that prevent you from getting any work but what they hand you.