Should have went vs Should have gone

'Went' is the simple past conjugation of the verb, 'go'. Saying

"I went to class, but..."

is correct because the you are simply explaining something that has already happened. However, in the case of

I should have gone to class, but...

you need to use the past participle. (The word 'have' is always a clue that you need to use the past participle.)

The reason this is confusing is because for most verbs the past participle corresponds to the simple past tense. (Ex. colored, advanced, helped, stopped) 'Go' is irregular, though, so you have to watch out.

See Past Participles on Udemy for a full explanation.

I think this is a common confusion of the past simple with the past participle.

Modal verbs (should, would, could, etc) are followed by a bare infinitive, and the past participle, not the past simple. It can be confusing in the case of irregular verbs, so I ask "Would you say 'should have been', or 'should have was'?"