When as a young boy I first started thinking about what I wanted to do when I grow up, my grandmother suggested I be a policeman.

As a lanky, probably dirty, towheaded six-year-old, I don’t know what attributes I possessed in her eyes that would have recommended me to that particular profession.

After learning at school about the sad plight of Ned Kelly, I actually thought at that age that police were the bad guys and those they pursued the good guys.

Thumbnail sketch for those of you who don’t know: Kelly reputedly robbed from the rich and gave to poor in colonial Australia, until his handmade suit of steel, like Robert Downey Jr.’s in “Ironman” – only more folksy – failed him in a stand-off with a trainload of lawmen.

So my grandmother’s suggestion didn’t really mesh. Motorcycle stunt rider held much more traction, until that gave way to sugarcane farmer, both inspired by who-knows-what.

But her advice came flooding back Thursday when I attended a forensics camp for middle school students put on by the Suffolk Commonwealth’s Attorney’s office.

Kids were wide-eyed as they combed simulated crime scenes for evidence in order to lock up crooks.

Joan Turner, who coordinates community outreach for the office, walked me through the devastating mock crimes, complete with knives hastily ditched, blood spatters and smashed windows.

Were the glass shards inside the room on the shag pile or outside the room amongst the marigolds? Those are the sorts of things to look out for.

Commonwealth’s Attorney Phil Ferguson reported strong interest in the second camp this year after the first one had a long waiting list.

It’s good to see this level of interest among youngsters in a challenging job for which society needs good men and women, and also that they’re being given a chance to learn more about it.

Driving back to the office, the forensics camp got me thinking about my grandmother’s advice. I’ve thought about what it would have been like to follow it at other times as well, like when reporting an interesting crime story.

My early notion of the roles assumed by police and criminals has since been disabused, of course, along with many other boyhood beliefs, including that the world is entirely safe and secure.

It’s not, and we need the people who rightfully make a living off the back of that — police, attorneys, judges, wardens and even, dare I say, reporters — because those who wrongfully do so will probably always be with us.