Tel: 63399009 This is the phone number of the Letters and Calls Office of the Education Bureau, which can also be said to be a report phone number.
Letters and visits are places where people petition for reasons and arguments, mostly within the local government.
This kind of thing, it is useless to find the local education bureau, teachers are hired through them, so I know this situation very well. I will definitely refuse you, or get some fake diplomas to cheat you. You must have the evidence! For example, their academic qualifications and their poor teaching ability.
I suggest you report to the Tianjin government at the next higher level.
/This is Tianjin Government Affairs Network. Complaints can be made in the "online service" or "mayor's mailbox".