I have the same situation with most of my students. I find the most helpful thing to do is drill pronoun variations with one or two simple sentences for the whole class. This ensures that they remember their pronouns and gives them a limited challenge in which they can be confident of what they are saying.
example: (psuedo-random order of questions and students; try to get every student to practice everything)
(Teacher) Who are you?/Who is he?/Who is she?/Who are they?/ Who are we?/ Who am I?/
or with colour variations and it/they/this/that/these/those
or with possesive pronouns and clothing colours
or with prepositions and simple vocabulary
or with 'what do you like' around the class, and then make a game out of who can remember the answers given by another student by asking 'what does he like?/What do they like?'
Another useful thing is to drill the 'W' question words (who what when where why and how (how is the backwards W word!)) that they have learned every day.
Teacher(around the class): Who are you? What are you? Where are you? How are you? (and with other pronouns as well)
Do this kind of stuff everyday! As the students learn and become confident with more grammar, the games can become much more complicated and competitive (if you set them up to be competitive, that is).
My students only come once a week so doing this is very important to reinforce their memories, I feel.
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