Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_67527 ( "Institution" text, "Team" text, "City" text, "Province" text, "First season" real, "Head coach" text, "Enrollment" real, "Football stadium" text, "Capacity" real )

### Question ###
What is the average capacity of stadiums in the City of London that belong to schools with an enrollment less than 30,000?

### Accurate SQL ###

SELECT AVG("Capacity") FROM table_67527 WHERE "City" = 'london' AND "Enrollment" < '30,000'