what is the meaning of the word "should"?

English as a Second Language English Vocabulary, Grammar and Idioms
1

She averted her face so that the child should not see her tears.

2

would

3

Is there any nuance between “should” and “would” here

4

Just the level of ‘politeness’.

5

She averted her face so that the child should not see her tears.
She averted her face so that the child did not see her tears.
What is the difference between them?

6

Just the level of ‘politeness’.