CREATE TABLE table_name_45 (level INT, leaguecontested VARCHAR, season VARCHAR)

Which Level has a League Contested of northern premier league premier division, and a Season of 2011 12?
SELECT AVG(level) FROM table_name_45 WHERE leaguecontested = "northern premier league premier division" AND season = "2011–12"
SELECT AVG("level") FROM "table_name_45" WHERE "2011–12" = "season" AND "leaguecontested" = "northern premier league premier division"