Vicky Allen, 51, told a 14-year-old autistic student she was unhappy with the way the Biblical rainbow symbol is used to represent gay pride.
She also told the student she did not approve of same-sex relationships.
On Monday at Bodmin Magistrates' Court Ms Allen will attempt to overturn the disciplinary action, which has left a formal written warning on her record for the period of a year.
The teaching assistant is also seeking compensation for injury to her feelings.
Speaking to The Sunday Times she said that: "He asked me what I believed, so I told him my Biblical beliefs."
The student was questioned by Brannel School and said that he had not been offended by the comments.
Vicky Allen works helping children with a range of educational challenges.
Andrea Williams, from the Christian Legal Centre, who is supporting Ms Allen, said "political correctness and fear" is eroding freedoms.
She told Premier: "She gave a straight answer because that's the kind of answer that's required in this situation with these children with special needs."
"My hope for Vicky is that the employer will see it overreacted, that the warning will be removed and that she will press on with an unblemished record in teaching," she said.
Premier has contacted the school.
Listen to Premier's Hannah Tooley speak to Andrea Williams here:
