Many parents seek speech therapy for correcting a lisp as it can sound a bit inappropriate, especially in older school-age children. As children develop their speech sounds, they progress through a certain number of speech processes. These are what we term ‘normal errors’ and we expect them to resolve naturally by certain ages.
A lisp is not a ‘typical’ speech error. It does not usually make a child’s speech harder to understand and will normally resolve naturally in the early years, but it is not possible to know for certain if this will be the case.