pet question / post!!!

okay so i have two kittens. i’ve had them since they were about 7 weeks. i’d say they’re about 4 months old. i have one of those food bowls that always has food in it and more just comes out when it’s empty enough. so they ALWAYS have food and they’re always eating. my problem is, they always are trying to get into human food! they climb up in my daughters high chair and try to eat her left over food! and if she has a snack they’re always trying to take it! we had pizza last night and i didn’t get a chance to clean off my daughters high chair until this morning but when i woke up there was a piece of pizza off her high chair on the floor in front of my couch! i know it had to of been the cats because my daughter didn’t eat any more after she was finished! does anyone know how i can break them of this?