The MOE has contacted some schools (at least mine in Chanthaburi has been 2 days ago) and apparently teachers currently on the amnesty can get an extension of their visa by going to immigration before the 11th of September. This extension would be valid only until the 26th of September which would be enough time (15 days ) to get it transferred to a non-B before the deadline. However, I've not seen any official confirmation, the only sources I have are a forum on Thaivisa and what my school told me and it isn't really clear what the requirements are. Also it seems it would only work for the immigration offices requiring only 15 days left on a hard stamp to get a non-B (some immigration offices require 21days). The best would be to ask your school to contact the MOE, the labour office and the immigration office.