Will a child end up with cancer if he has a habit of eating chalk?!
Most likely he has pica. Its not a big deal really but it warrants a trip to the Dr. Pica is only a vitamin or mineral defeciency in the body that makes us crave weird things. When I was prego, I ate chalk too.
If your kid stuck pennies into his wazoo would you let him do that? If my kid ate chalk regularly I'd slap him silly. Chalk may be mineral rich, but I'd bet it has carcinogens. Don't ever eat chalk.
Most chalk is just calcium carbonate, not a big deal if eaten. In fact, it's used in many antacids. You should take the kid to the doctor though, and make sure (s)he doesn't have some sort of digestive problem, or mineral deficiency. It's probably fine though.
Minored in Biology
Nope, so far chalk and cancer have not been conclusivly related.