writing paragraphs

I had Clay write two paragraphs about his brother's visit. He had two solid topic sentences and maintained his topic throughout, but I noticed he's not utilizing the information we've gone over. For example, he's excellent at spotting a run-on sentence on a worksheet, but had at least 4 run-ons in his paragraphs. He's still working on using complex and compound sentences, but is improving in that regard. He needs to focus more when he writes.