Complex sentence: When he was younger, he was accused of a convenience store robbery, but the charges were dropped soon after, still he was incarcerated at a penitentiary, which didn't allow him to graduate high school.
Split into simpler sentences: When he was younger, he was accused of a convenience store robbery, but the charges were dropped soon after. Despite this, though, he still he was incarcerated at a penitentiary, which didn't allow him to graduate high school.