This will really speed things up:
ALTER TABLE _ISO ADD KEY(_objective_id)
If you do an EXPLAIN on your current query, you would see that no index is
used for the _iso table so the engine has to do a table scan. And, for
future reference, the output of SHOW CREATE TABLES is more informative
tha
SELECT
_objectives.id,
_objectives.name,
COUNT(go._iso._objective_id)
FROM go._objectives
INNER JOIN go._subjectHeadings
ON go._subjectHeadings.id = go._objectives.subjectHeadings_id
INNER JOIN go._subjects
ON go._subjects.id = go._objectives.subjects_id
LEFT JOIN go._iso
