What is the grammar mistake in this sentence complementary admission for teachers and students?

It should be COMPLIMENTARY ADMISSION FOR TEACHERS AND STUDENTS.

The explanation I can provide about the sentence is that it means that for both teachers and students admission is free or "compliments of the house." . On the contrary, the word complementary refers to the fact that the teachers and students complement or even support each other. So that, the word complementary in the sentence changes the entire meaning or message conveyed.

im not entirely sure what you're asking.

d when mathilde realizes she has lost the necklace