Studies from the U.S. National Education Association say that giving students homework over the weekend leads to a build up of stress during a time when students are meant to relax and unwind. The same is true for giving students homework over school holidays, such as winter break.
Studies performed by the U.S. NEA do not recommend that teachers just avoid giving kids homework over the weekend. The association also recommends that teachers not give more than 10 minutes of homework per night, per grade level. Assigning more homework cuts into a child's free time and leads to a buildup of stress.
In general, homework has fallen out of favor with teachers and students alike. In 1901, California established a law that limits the amount of homework that teachers are allowed to assign. Much of this has to do with the fear that assigning too much homework keeps kids inside and contributes to childhood obesity. It also keeps some kids from participating in extracurricular activities because they have to focus on their studies. Although the U.S. NEA agrees that schoolwork is important, it also agrees that there needs to be a clear cut off time when schoolwork ends and free time begins.