1. It is necessary for children to be taught manners.[passive infinitive]
2. Manners should be taught to children.[modal passive]
3. Children should be taught manners.[modal passive]
Are 1 and 2 sentence structure meaningfully same or different(let go little difference between necessary and should)? I think, it is same.
I made 3rd sentence as same meaning with 2 sentence with different structure . Is it right?
They are all correct, with no significant difference between them.