Write SQL query to solve given problem: What is the average education level of customers from the place with the highest average income per month?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT AVG(T1.EDUCATIONNUM) FROM Customers AS T1 INNER JOIN Demog AS T2 ON T1.GEOID = T2.GEOID ORDER BY T2.INCOME_K DESC LIMIT 1