This is 100% happening and even for AP and high level classes. There is a pipeline of teachers from a handful of countries--Filipinos and Jamaicans, for instance--into US public schools.

It's not all bad. I would by far prefer American born and educated teachers who are not nuts. THey are becoming a rarity. In highschool my best teacher was a US and World history teacher who had a PhD in history and, importantly, NO EDUCATION DEGREE. Smart individuals who are well-trained in their topics are the best teachers, imho.

The worst are those with education degrees, or even multiple education degrees, and nothing else. That can work for young childhood education (elementary school) but not much beyond that.

My oldest kid has had 3foreign highschool teachers. There was a Jamaican history teacher (bad), a Filipino Biology teacher (good!), and another Filipino math teacher (TBD).

The good thing is that they don't necessarily come with the same ideological baggage that education degreed Americans do, and they work hard in the classroom to get good results in order to maintain their job and immigration status.