This sounds almost the same as the school/company I worked for a in Ulsan called 'YES English Academy' in OK-Dong. They too did the things you said + many many other things such as:

1. They stole money from foreign teachers' paychecks.
2. They stole all the foreign teachers' passports & refused to give them back until they were threatened with the Ministry of Labor. They took them because they "didn't want any foreign teachers to run away".
3. They tried to sack my co-workers just before the end of the contract to try and cheat them out of their severance pay and flights.
4. They went into multiple teachers housing and searched through their personal belongings (they also admitted to this when confronted)
5. Mr. Kim (the owner) repeatedly tried to persuade foreign teachers to not get medical insurance so that they did not need to pay.
6. They harrassed foreign teachers at home when they are ill off work (depsite doctor's note). This even occurred when my friend/co-worker was off with stress due to his father dieing.
7. They repeatedly did not pay the teachers' taxes to the government & pocketed the money themselves.
8. They did not allow holiday allowance given in contract.
9. They did not provide any materials for teaching - it was often difficult to even have a book for the class.
10. They tried to deduct more money etc from teachers' wages, even though not in contract.
11. Mr.Kim (the owner) openly stated that he had "no respect for foreigners" and is "prejudice" towards them.
12. Poor/dirty housing conditions.
13. Education and effective teaching methods were last priority, if considered at all.
14. The recruiter and owners/directors lied to different people and couples that they would be working in the same schools, however when they arrived they were told that this was no longer the case.
15. Illegally took "holding money" away from the teachers' paychecks to discourage them from running away.
16. Deducted money from severance pay without teachers' consent.
17. The 'head director' Stacy would interrupt your class to shout at you in front of your students for irrelevant matters such as if one of them (students) was not sitting up straight enough.

There are much better schools out there which would give newcomers to Korea a more positive experience. I hope people learn from the mistakes of others and give this company and yours a miss.