Opposition comes from varied sources, including organizations of teachers and school districts. The National Education Association – a teachers' union, and the largest labor union in the United States is on record as opposing homeschooling outright, though in recent years it has not been as outspoken.
Opponents state concerns falling into several categories: academic quality and completeness; reduced funding for public schools; lack of socialization with peers of different ethnic and religious backgrounds; fear of religious or social extremism; that homeschool curricula often exclude critical subjects; that parents are sheltering their children, or denying them opportunities that are their right such as social development, or providing an unfair advantage over students whose parents lack the time or money to homeschool.
There are studies that conclude that homeschooled students do extremely well on average on standardized tests. However, these studies generally compare voluntary homeschool testing with mandatory public-school testing, because the study organizers cannot require testing. Some states require testing for homeschooled students and some do not; many that do require testing let homeschooling parents choose from more than one evaluation method. The demographics of homeschooling are difficult to compare to traditional schools, or even to define. Agencies, parents, and studies may disagree as to which students "count" as homeschooled. Some people have argued that homeschooled students, especially those who are likely to be tested, are an atypical group whose parents care strongly about their education and would also do well in a conventional school.
Some scholars see potential civic dangers in certain forms of homeschooling. Robert Reich, for example, writes that homeschool can potentially give students a very one-sided view of things, as their parents may, even unwittingly, block or diminish all points of view but their own in teaching. This may make students unable to think for themselves or to adapt to multiple points of view. He also argues that part of being a citizen is having something in common with fellow-citizens, and homeschool diminishes that by reducing students' contact with peers. In short, while homeschooling can be good, Reich warns that those practicing it must avoid these dangers.
Gallup polls of American voters have shown a significant change in attitude in the last twenty years, from 73% opposed to home education in 1985 to 54% opposed in 2001.