Anyone who has taught grammar in a beginner level ESL or EFL class knows the speed and accuracy with which students complete grammar worksheets is only weakly correlated with their ability to use the grammatical structure in their own speech.
Take the verb “to go” in a beginner class. No matter how many times students complete worksheets where they determine whether to write go or went, when they speak, they frequently forget to use “went” when speaking about past events. This might have to do with what Stephen Krashen called the order of acquisition. Or maybe it has to do with the fact that verbs in the students’ first language may not change form in different tenses.
I think the main reason is we generally use our ears to tell us when something is wrong, not our reasoning minds. It has to sound wrong before students will correct themselves. It’s hard for something to sound wrong when students at the beginner and lower intermediate level have been exposed to so little comprehensible input in the target language.
I use this sign for GO and WENT when teaching the past tense:
I put it up temporarily on the board when I’ve asked students to talk about where they went yesterday or last weekend. Each time they use “go” when “went” is required, I tap on the sign. Pretty soon, I have the whole class calling out “went”. They are hearing it, too now, and are starting to correct themselves.