you can wait for one or two years .but get his regular check up done every monthly.

Hello Child have a tendency to accommodate to see clear That's why we always instill eyedrop before checking the power of eye in children In certain situations like when  child accommodates to see clear we prescribe glasses Kindly share his glasses prescription and his case file so that I may guide you better Regards

You should follow ophalmologist 's advice

The refraction of children must include instillation of cycloplegic and a post mydriatic test a few days later. (so that any error due to excessive accomodation can be eliminated) Your child reading 6/9 and an adult reading 6/9 is not the same thing because accomodation plays a major role in children, which prevents us from finding out what the real vision is when accomodation is relaxed. Please post your childs glass prescription so that v van guide u better. Otherwise u may take a third opinion... consult a pediatric ophthalmologist if possible as they will be more experienced in testing vision and doing refraction in small children.