Database: world_1
Question: Give the mean life expectancy of countries in which English is not the official language.
SQL: select avg(lifeexpectancy) from country where name not in (select t1.name from country as t1 join countrylanguage as t2 on t1.code  =  t2.countrycode where t2.language  =  "english" and t2.isofficial  =  "t")