@Garrett **********
you actually do have to pass a ministry of education exam on Thai language after your first ED extension.
Normally it's at the ministry, but because of Covid they've been letting the schools administer the test instead, so it's kind of pointless at the moment. But if they go back to the ministry tests, the visa mill schools will be pretty useless for more than those wanting to stay more than 6 months without putting in any effort.
Every ED visa extension requires paperwork that the school gets from the Ministry of education as part of the packet you take to immigration with you.