Two sisters were sent home from school for wearing cancer charity badges in support of their terminally ill grandfather.
The sisters wore the daffodils to school in support of their 69-year-old grandfather, David Paggiosi, who has inoperable bile duct and abdomen cancer.
A letter from acting principal Richard Brooke at Outwood Academy City, Sheffield, said: "I am writing to inform you of my decision to exclude Elise Casey for a fixed period of 1 day(s). This means that they will not be allowed in the Academy for this period.
"I realise that this exclusion may well be upsetting for you and your family, but the decision to exclude Elise has not been taken lightly.
"Elise has been excluded for this fixed period because she refused to follow a reasonable request from a senior member of staff.
"I must advise you that you may receive a penalty notice from the local authority if your child is present in a public place without reasonable justification."
Mum Gina, 42, told her local paper: "I'm so angry about the way the school has handled this. I don't agree with it because it doesn't affect their reading and writing and it is in support of their granddad who they are very close to.
"It upset my dad because he knew they were doing it to support him. They were distraught and are finding it hard to come to terms with what is happening to their granddad."
The girls' dad, Lee, 42, added: "They really should have taken their circumstances into consideration - it wasn't like they were wearing One Direction badges, the daffodils are for a very, very good cause."
School staff said it has strict rules about pupils wearing charity badges on their school uniforms - although they are allowed on bags, bag straps or outdoor coats.
Gina said: "The girls had comments from teachers the week before and one teacher made the youngest take the badge off.
"They were sent straight home from school last Monday [October 20] after being excluded for a day. The school rang me and I went home to find them sitting on the doorstep as they didn't have a house key."
A spokesman for the Outwood Grange Academy Trust said: "We have an excellent track record of supporting a wide range of charities and encourage students to take part in charitable events and activities.
"Our policy is to request students to wear charity badges on either the bags, bag straps or outdoor coats but not as part of their school uniform.
"The only exception to this is when students purchase a poppy in the weeks leading up to Remembrance Day."