If white teachers don’t like it, they can stop teaching.
There aren’t enough nonwhite teachers to keep the system running for a single day if the white teachers quit.
I don't know about other parts of the country, but here in Los Angeles we only seem to comprise about 25% of the district's teachers. Most of LAUSD seems to be Hispanic. (Of course, whether or not a Hispanic is white depends on if they are being deported or shooting Trayvon, so... I dunno.)