omit as in passive

[aysaa]

Hi,

1. The regime was inevitably labelled as 'communist'.

2. Michael was considered as an excellent teacher.

3. She is known as a teacher.

I would like to know if the adverb 'as' is necessary.

Thanks.

 

[Rover_KE]

It's not necessary in 1 and 2, but it is in 3.

 

[saloom2]

In general, when does 'as' become necessary??