diff --git a/README.md b/README.md
index 87783946..3f76d339 100644
--- a/README.md
+++ b/README.md
@@ -93,7 +93,7 @@ mysql -u root -h 127.0.0.1 -P 4000
 ```
 ## Autograding and certification
 
-Since Jun 2022, we start using [github classroom]([https://github.com/talent-plan/tinysql/classroom.md](https://github.com/talent-plan/tinysql/blob/course/classroom.md)) to accept labs and provide autograding timely. The github classroom invitation is https://classroom.github.com/a/cdlNNrFU. The discussion Wechat/Slack group and the certification after you pass the class is provided in the [tinyKV learning class](https://talentplan.edu.pingcap.com/catalog/info/id:263)
+Since Jun 2022, we start using [github classroom](https://github.com/talent-plan/tinysql/classroom.md](https://github.com/talent-plan/tinysql/blob/course/classroom.md) to accept labs and provide autograding timely. The github classroom invitation is https://classroom.github.com/a/cdlNNrFU. The discussion Wechat/Slack group and the certification after you pass the class is provided in the [tinyKV learning class](https://talentplan.edu.pingcap.com/catalog/info/id:263)
 
 ## Contributing