Google Forms has built-in score importing for Google Classroom using the “Grade importing” option for assignments.
Form Presenter – Automatic Scoring and Importing to Google Classroom
Form Presenter is an add-on for Google Forms that provides additional controls for online assessments.
Quizizz – Automatic Scoring and Importing to Google Classroom
This article focuses on how to integrate Quizizz with Google Classroom so student scores on assignments are automatically passed into Google Classroom.