A school in Texas has been flooded with donations after a teacher shared a heartbreaking letter to Father Christmas written by a first-grader, who asked only for a blanket and food for Christmas.

Ruth Espiricueta, a teacher at Monte Cristo Elementary school, asked her pupils to write the letter to Santa as an exercise designed to teach the children the difference between "wants" and "needs".

The letter written by a 7-year-old girl read: "I have [been] good this day. This Christmas I would like a ball and food. I need a [blanket]."

Moved by her student's plight, Espiricueta shared the letter on social media.

Posting the note on Facebook she wrote: "This makes me very sad. When your students ask for food, blankets, or a bed instead of toys As a teacher it breaks my heart when I hear them ask for things that we sometimes take for granted. Hopefully I will be able to fulfill at least one of their Christmas wishes."

The post prompted others, who were similarly moved, to make donations to the child and other students. 616 blankets have so far been sent to the school.

Following the public outpouring, Espiricueta told ABC News she was unaware of her student's personal difficulties.

"I had no idea she was going through hard times being that she is always at school with a big smile. Her act of unselfishness made me realize that I needed to share this with others."

She explained that many of her students face similar difficulties. "Some of my students were not even excited about Christmas because they know that their parents cannot afford to buy a Christmas tree or gifts for them."

Members of the public in the local community have rallied together on social media to collect donations for the child and her family.