A supply teacher's call to police about a six-year-old Muslim boy with Down's Syndrome led to his family being investigated for terrorism.

Officers launched the probe after six-year-old Mohammad Suleiman allegedly kept repeating the words "Allah" and "boom" class.

His parents from the Texan city of Pearland, around 20 miles south of Houston, have claimed this cannot be true because "he doesn't speak at all" and has "the mental capacity of a one-year-old."

The boy's father said the family been through hell after becoming the subjects of both a police and social services investigation.

"The last three or four weeks have been the hardest of my life," Maher Suleiman told the Fox26 news channel. "My wife and kids were crying a few days ago and I told them everything is fine.

"Mohammad was born with Down's Syndrome Chromosome 21. He needs care all the time."

He added: "They claim that he's a terrorist. This is so stupid, this is discrimination actually. It's not implied discrimination, it's a hundred per cent discrimination."

The teacher was covering for a regular member of staff at the CJ Harris Elementary School when he made the call.

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