diff --git a/13.sql b/13.sql
index e69de29..89cee9d 100644
--- a/13.sql
+++ b/13.sql
@@ -0,0 +1,21 @@
+-- write a SQL query to answer a question you have about the data! The query should:
+--
+-- Involve at least one JOIN or subquery
+-- Which schools have the highest graduation rates in districts that spend less than the average per-pupil expenditure?
+SELECT
+    s."name" AS "school",
+    d."name" AS "district",
+    e."per_pupil_expenditure",
+    g."graduated"
+FROM "schools" AS s
+JOIN "districts" AS d
+    ON s."district_id" = d."id"
+JOIN "expenditures" AS e
+    ON d."id" = e."district_id"
+JOIN "graduation_rates" AS g
+    ON s."id" = g."school_id"
+WHERE e."per_pupil_expenditure" < (
+    SELECT AVG("per_pupil_expenditure")
+    FROM "expenditures"
+)
+ORDER BY g."graduated" DESC, s."name" ASC;