How old is he? When you talk about sentence construction, are there patterns behind what he is doing- does he regularly do the same thing? When learning languages, children often over-apply rules and come out with the wrong form, and then modify the rule to account for the new information. A commonly quoted example is a child saying 'bringed' because they have learned the -ed for the past but not mastered irregular verbs- when they get feedback and learn, then they learn not to add -ed to all verbs. If you could post some examples, it would be easier to be less vague. (By rules, I mean the rules that native speakers acquire subconsciously and not the rules found in grammar books, etc.)
By the way, with your list of sentences idea, it is worth bearing in mind that in isolation they could help with basic word order but would lack the cohesion and devices required for texts.
Some of these sites might be able to help: Special Educational Needs - ESL Web Directory - UsingEnglish.com
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