No, I do not think that educational vouchers enable strong accountability and standards, and instead create an atmosphere where students keep leaving schools for better schools which increases class sizes. Students should be able to stay at the school closest to them, and let the district figure out the best way to educate them without using vouchers.
Although it's true that having no profit motive for schools doesn't necessarily breed any sort of incentive or competition, I don't think schools are the right place for competition but rather should be for cooperation. A voucher program would simply inflate whatever issues currently exist in our education systems. Exploring other options would be preferable.