u/chick-a-dee-dee-ME

Howdy all. I have about 20 students and all have been progressing in their speaking abilities very well, all but one. They are a 9 year old child and their only exposure to English is with me, twice a week for 1/2 a lesson. They are slightly better at reading and the most basic grammar but often they are just guessing. I feel, without any time outside of their lessons listening, reading or speaking English, I am wasting their(parent's) time and money. They do no homework at all. The child likes me and I do make the lessons fun but I have been working with them for 6 months and they have made barely any improvement. They still mix up b's and d's! Any advice is welcome.

Some of my students have requested workbooks. I am used to creating lessons and don't use them. Any recommendations? I teach English.