Children as young as nine have asked for counselling after being described as "terrorists" by their schoolmates, the NSPCC has said.
It comes Childline, the charity's confidential advice service, reported a spike in sessions concerning racial- and faith-based bullying following the Westminster Bridge terror attack.
Counsellors said they had run more than 2,500 sessions in the last three years on the subject, with under-19s from a range of religious and ethnic backgrounds getting in touch.
Students who contacted the service described being called "terrorist" or being bullied for being a Muslim.
An NSPCC spokesman said: "For children as young as nine to be bullied because of their race or faith is extremely worrying as we know just how damaging bullying can be.
"Children may not realise just what an impact these hurtful words and actions can have, but bullying can lead to mental health problems and even self-harm.
"It's vital that an adult intervenes if they see a child being picked on and nip this behaviour in the bud."
The charity said it received 128 counselling session requests in April following March's Westminster terror attack - up from 71 the previous month.
And there were nearly 300 sessions with children concerned about terrorism in the two weeks after the Manchester Arena attack.
Childline also reported spikes in the wake of the Paris and Brussels disasters.