Any legally established uses existing prior to the effective date of this chapter, which are allowed within a particular zoning district as a special permit or a special exception use by the provisions of this chapter, shall not be deemed to be a nonconforming use in such district. However, excepting existing places of worship and schools, any subsequent replacement or enlargement of such use or of any building in which the same is conducted or the construction of any additional building for such use beyond the extent which existed prior to the effective date of this chapter shall require a special permit or special exception obtained in accordance with the provisions of this chapter. (Existing schools and existing places of worship may expand, remodel or rebuild, provided that such is on the existing lot and complies with all health, highway and building code requirements.)