Don't be fooled. There are no guarantees. You can't sit back and wait for the government or the school system or the enforcement agencies to do something about the drug problem. You have a significant role in your child's life, and you have to accept that role and do something. I think the single-parent stereotype suggests that.
Truth is, the quality of parenting makes a huge difference, too.
In some two-parent households, neither parent spends time with the child. But a parent needs to realize that two of the 30 or so identified factors that have been linked to susceptibility to drug usage are divorce and growing up in a single-parent home. A child can be affected by any combination of those factors, which were determined in part by the U.S. Department of Education and the National Commission on Drug-Free Schools, among others. What magnifies the problem is if a single mom or dad does not have the time to be involved with his or her child or to notice what's happening. Mainly, a very solid concept of what is right and what is wrong.