The U.S. Drug Enforcement Agency says marijuana is harmful, which is why it's illegal. The agency also says legalizing drugs will lead to more use and addiction.
Despite the disparity between federal law and the law of some states, policy experts say the public is becoming more accepting of legalized medical marijuana and there's a better consensus between the public, legislators and those who sell medical marijuana.
"Twelve states are now considering laws, and each state is learning from the mistakes of others," said Morgan Fox, a spokesperson with the Marijuana Policy Project, an organization working to increase support for legalization of marijuana. "As other states have encountered problems, they are learning more that governments can work with people to deal with issues that come up."
Medical marijuana advocates say growers and producers are working on their own ways to educate people about responsible use of the drug.
"A lot of dispensaries are giving people literature, there's another group going around putting on conferences talking about the different ways of consuming it, and there's a better understanding about the need to better labels on it," said Chris Conrad, an author and medicinal marijuana advocate.
Advocates are trying to prevent incidents like the one at the Vallejo elementary school.
"Most people are trying hard to avoid this kind of situation so they don't attract federal scrutiny," said Robert MacCoun, professor of law and society at the University of California, Berkeley. "Local communities are very involved in regulating medical marijuana."
Conrad said despite what responsible adults do, the message to kids should be clear.
"The only reason to use marijuana is if you need it for a medical reason."