> Would a strong negative correlation between number of non-English speakers at a school and school performance convince you?

Somewhat, once also adjusted for funding per student, pay of teachers, all those other factors.

> And then once you have been convinced what will convince you that the most just and moral approach is strict border security?

There's a difference between strict and inhumane border security. You act as if we have to pick one. I don't think you'd ever convince me on that front because I can picture so many better options to this policy. There is no obligation or moral requirement that we cause this harm due to lack of any other options.