Hammaad Munshi was only 15 when he was recruited into a worldwide conspiracy to wipe out non-Muslims, and longed to go abroad and fight.

His parents in West Yorkshire were shocked when police found al-Qaida propaganda promoting "murder and destruction" on his PC and notes on martyrdom hidden under his bed.

Yesterday his grandfather, Sheikh Yakub Munshi, president of the Islamic Research Institute of Great Britain at the Markazi Mosque, Dewsbury, backed the sentence but warned that the same thing could happen to any family.

Their local MP, Shahid Malik, said the case should act as a "wake-up call" to parents about what their children might be getting up to on the internet.

Munshi, a GCSE student, led a double life, obediently attending school by day and surfing jihadist websites at night. He was part of a cell of cyber groomers devoted to brainwashing the vulnerable into killing "kuffar", or non-be-lievers. He was arrested, aged 16, on his way home from school.

Munshi, now 18, of Greenwood Street, Savile Town, Dewsbury, was found guilty last month of compiling information likely to be useful in terrorism. Blackfriars Crown Court, London, heard that he downloaded files about making napalm, detonators and grenades for himself, Aabid Khan and Sultan Muhammad, from Bradford. They were jailed last month.

Judge Timothy Pontius, sentencing Munshi at the Old Bailey yesterday to two years in a young offender institution, said: "You have brought very great shame upon yourself, your family and your religion."

He had fallen "under the spell of fanatical extremists... Khan in particular. They took advantage of your youthful naivety in order to indoctrinate you with pernicious and warped ideas masquerading as altruistic religious zeal."

Harendra de Silva QC, for Munshi, said he had been subjected to "grooming and manipulation" His relatives were "devastated" by what had happened "not least because of the shame that it has brought upon this very upstanding family".