Write SQL query to solve given problem: When was the project with the highest quantity went live on the site? Indicate the grade level for which the project materials are intended.. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T2.date_posted, T2.grade_level FROM resources AS T1 INNER JOIN projects AS T2 ON T1.projectid = T2.projectid ORDER BY T1.item_quantity DESC LIMIT 1