Behind these two photos is the sad story of a primary school teacher's downward spiral.

Heroin’s life-destroying effects are perfectly captured in photos of a US primary school teacher before and after her drug-fuelled downward spiral.

Megan Sloan, 27, is facing one count of child neglect among other charges after she was forced to leave her teaching position after bringing heroin and syringes to school, NBC reports.

Sloan was arrested on May 1 after a colleague at Holmes Park Elementary School in Tulsa, Oklahoma claimed he caught Sloan talking about selling heroin and pawning school property on Facebook.

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Heroin, methamphetamine, prescription drugs and 40 syringes were allegedly later found in her handbag, which had been left in her classroom, NBC reports.

On Tuesday a charge of child neglect was added to allegations of drug possession and embezzlement. She is suspected of using money intended for a school trip to buy drugs and pawning school property such as iPads.

The news of a teacher – only caught when she left her Facebook account open on a computer at school – bringing drugs to school is shocking enough.

But it’s the comparison of her mugshot and personal photos that has all who see them horrified.

The clear-skinned, smiling face of Sloan's Facebook photo is a stark contrast to the tired, blemish-ridden one in her mugshot.

Truly a picture tells a thousand words - this time of the harsh realities of drug addiction.