the issue is that the school_ID column is set to be the Index Column.
you should not be entering anything in the index column.
the index column should be the primary key column in your database.
You should set the primary key column to be an auto number column so that the database will assign it a unique ID.
Set the school_Id to be an auto increment column in the database and let the database handle giving the school an id.
the error is occurring because your page is missing the following line:
<?php require_once("../WA_DataAssist/WA_AppBuilder_PHP.php"); ?>