I HIGHLY recommend Mexican Blacks. My first snake was a Mexican Black, and he is so great I have a couple more snakes now, too. We raised Vincent from a hatchling, and never had any problems with him. He's so gentle my daughter handled him from the time she was 7 years old (folks loved seeing my petite daughter at 10 years old with a big shiny black snake coiled all around her waist at educational shows). He's still the one I choose when having newbies handle one of my snakes, because he's so trustworthy. He's gone to many schools and educational shows over the years, and my only concern has been that he's not hurt, not the children (had one kid squeeze him before I saw what was happening; Vincent tightened on my arm - I always have his head and upper body on me, reptile society rules - and I removed the child's hand from Vincent with a gentle reminder that snake's feel pinches, too; but Vincent never even tried to strike).
If you've already raised a corn, you're certainly able to raise a Mexican Black, and have a wonderful time with it. 
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1.0.0 Dumeril's Boa, Bruce
1.0.0 Mexican Kingsnake, Vincent
1.0.0 Graybanded Kingsnake, Boris
1.1.0 Ball Pythons, Pete & Frank
2.3.0 Bearded Dragons, Bela, Sally, Caijun, Phoenix & Spook
0.1.0 Fattailed Gecko, Sahein
2.0.0 Rats, Captian Howdy & Despero
1.0.0 Pushy Lovebird Baxter