You cannot execute SQL statements directly from a bash script. Use
psql to send the command to the database server. If you have a single (or a few) SQL statements to execute you can do it like this
psql -d YOUR_DB_NAME -c "YOUR_SQL_STATEMENT"
Make sure that your SQL statement does not include quotes or escape them appropriately. If you have many SQL statements in a file you can execute all of them like this
psql -d YOUR_DB_NAME -f FILENAME
In the above YOUR_DB_NAME should be replaced with your database name, YOUR_SQL_STATEMENT with the SQL statement you want to execute and FILENAME is the name of the file with SQL statements to be executed.
If you need to specify extra parameters like username, check the command's usage message displayed with
Also, note that your syntax for
DROP SCHEMA is incorrect. It should be
DROP SCHEMA IF EXISTS schema_name;
See also this documentation.