Nowadays, Escalante works primarily in the private sector where success matters more than politics.
Money matters more than success in the private sector. Privatization is not a panacea. It has a different set of problems than publicly funded and controlled schools. I don't know if the argument is for using private schools with tax money, or to privatize the entire public school system, so I'll try and address both.
Vouchers fail on several levels. They often do not pay the full tuition for a private school, which still leaves low-income kids with no option but public school. The rich kids that go to private school anyway get a discount on their education and syphon away tax dollars from the poor kids at the public school. The rich get richer, the poor get a worse education than before. It does however help the middle class, a lot, since they could probably cover the difference but not the entire tuition.
As far as totally privatizing all public schools, I think its a bad idea. I've been to two private schools, one that truly cared about education and the students, and one that truly cared about profit and inflating their statistics in order to maximize government funds. Special needs and bilingual students cost a lot of money and privatized public schools would avoid them like the plague, and along with troublemakers and underachievers, they'd be bounced around from school to school.
Also, you're not telling the whole story about Jaime Escalante. He pissed the union off because his class sizes exceeded the limit of 35 in their contract, some of his classes had 50 people. I happen to agree with limits on class sizes, and the union had to keep the limit in place to protect the other teachers, a classroom of 50 can be a dangerous, let alone unproductive, environment. His local school district refused to give him more teachers to teach all the students he wanted to, because of lack of funds, so instead of taking less students, he left. I think the real reason for him going to a private school is because they have the money to do what he wanted to do to teach kids, and probably to capitalize on his fame. Don't blame unions for all of the world's problems, he worked in a poor school, tried to teach too many people, and they, surprisingly enough, didn't have the money to do it.
Don't get me wrong, there are problems with public schools which are entirely their fault. There needs to be much more public and government oversight, otherwise they'll continue to do silly things like spend a million dollars on a football field (happened in Texas I think). I've been to an awful public school (in a poor town) and an excellent public high school (in a rich town). They both cry poor, the school in the rich town gets an order of magnitude more money than the poor town, but its not the sole problem. The administration in the poor school were frivilous with what they had, and cared more about sports. When I left, the parents that paid attention were pissed off and some people got fired, but I don't think anythings changed there. It could be a function of the rich town having more active parents in the PTA, more oversight over what the school spends money on. But look at how much more money a rich town can spend per person, theres a huge, huge gap. The rich town gets more money from local taxes and the same amount of state money as the poor town. Should the rich town be punished for having more revenue? No, but the poor town should get something more to even things out.