Some teachers feel very insecure in their jobs and dislike the idea of a new program that could potentially mean they are going to get cut, I think if districts properly explained the voucher system to teachers and what it meant to their job security you would see more teachers not be as against them as they are now.
Much as we hate to think this, teachers today are very protective of their jobs, pay, and schedules that no one else in the job market has. So if people have a chance to easily transfer their kids to a private school, public school teachers are going to be against this and see it as a threat.
Public school teachers oppose vouchers because they are forced to compete in a market where they were previously the monopoly. If students have the option to go to a school where the teachers are better, they will. This 'invisible hand' forces teachers to actually be good at their job instead of just showing up and handing out worksheets.
I believe school vouchers do put a teachers position in danger given that school systems may not need as many teachers if more students attend private schools. I honestly believe teachers should stay out of this discussion however because they would have biases involved, such as this problem. I'm personally against the voucher system myself, but I would be interested in hearing valid points from the other side.
Many teachers oppose school vouchers because it will take
money out of the public school system and use it to subsidize the private school
system. The public schools are already terribly
under-funded in many school districts, to the point that parents hold bake sales
and raffles for needed supplies. So
taking money away and giving it to private schools through the use of vouchers
is a really bad idea.