This large number of guns could lead to accidental shootings, especially those involving younger children who do not understand what guns do." To diminish school shootings all together there are many preventative measures that can be taken such as:   In a 2013 research report published by the Center for Homicide Research, they find that many also reject the idea of having armed classrooms due to what is termed the "weapons effect", which is the phenomenon in which simply being in the presence of a weapon can increase feelings of aggression. "In Berkowitz & LaPage's (1967) examination of this effect, students who were in the presence of a gun reported higher levels of aggressive feelings towards other students and gave more violent evaluations of other students' performance on a simple task in the form of electric shocks. This finding points to possible negative outcomes for students exposed to guns in the classroom (Simons & Turner, 1974; Turner & Simons, 1976)." In 2008, Harrold Independent School District in Texas became the first public school district in the U.S. to allow teachers with state-issued firearm-carry permits to carry their arms in the classroom; special additional training and ricochet-resistant ammunition were required for participating teachers. Students at the University of Utah have been allowed to carry concealed pistols (so long as they possess the appropriate state license) since a State Supreme Court decision in 2006. In addition to Utah, Wisconsin and Mississippi each have legislation that allow students, faculty and employees with the proper permit, to carry concealed weapons on their public university's campuses. Colorado and Oregon state courts have ruled in favor of Campus Carry laws by denying their universities' proposals to ban guns on campus, ruling that the UC Board of Regents and the Oregon University System did not have the authority to ban weapons on campus. A selective ban was then re-instated, wherein Oregon state universities enacted a ban on guns in school building and sporting events or by anyone contracted with the university in question. A commentary in the conservative "National Review Online" argues that the armed school approach for preventing school attacks, while new in the US, has been used successfully for many years in Israel and Thailand. Teachers and school officials in Israel are allowed and encouraged to carry firearms if they have former military experience in the IDF, which almost all do. Statistics on what percentage of teachers are actually armed are unavailable and in Israel, for example, the intent is to counter politically motivated terrorist attacks on high value, soft targets, not personal defense against, or protection from, unbalanced individual students. The National Rifle Association has explicitly called for placing armed guards in all American schools.