There are many high school reforms being proposed, so it is hard to know which one or ones you are asking about. I will focus on the impact of high stakes testing for high school students.
This reform is meant to help students by ensuring that they will have a strong base of knowledge and competence. The problem is that it also (particularly when test scores are tied to teacher pay) encourages teachers to obsess about the test and to teach to the test. Today, one of the greatest strengths of American education is that it generally turns out more creative people than the kinds of rote learning systems that many other countries use. This creativity has helped to give the US a very innovative economy. With the greater emphasis on testing, we may (if we do the reform as well as possible) get students with more knowledge, but we will lose some of the flexibility of thought and the creativity that are also vital for our economy.