Secondary school students achieve broad mastery of the curriculum if they are taught with methods appropriate to their learning styles and they devote significant effort to their studies.
ideo Explanation">
Conclusion
If broad mastery isn't achieved by students in a certain secondary school, then we know they weren't taught with method appropriate to their learning styles.
Evidence
If secondary school students are taught with methods appropriate to their learning styles and devote significant effort to their studies, then they will achieve broad mastery.
Evaluate
The premise is a conditional with an AND in the trigger.
Taught with approp meth and → Broad mastery Devote signif effort
The contrapositive: ~Taught w/ appropr meths ~Broad Mastery -> or ~Devote signif effort
Our author's conclusion resembles this contrapositive, only it is saying
~Broad Mastery -> ~Taught w/ appropr meths
That's cheating! Given a rule like, A → B or C I can't just go around concluding that A → B
It would be like saying this:
Our one possible objection to this argument is, "Hey, author, if broad mastery isn't achieved, it might be that they weren't taught with appropriate methods or it might be that they didn't devote significant effort (or both).
How can you so confidently conclude that if they don't have broad mastery, they definitely didn't have appropriate methods?
Goal
We need an answer to eliminate the other idea in the Or outcome.
The author established that if broad mastery isn't achieved, it's either because of inappropriate methods or lack of sufficient effort. To prove her conclusion that it always shows a lack of appropriate methods, we need to rule out the possibility that it's because of a lack of sufficient effort.
If we know these secondary students DID devote significant effort and they still didn't achieve broad mastery, then we would have to blame inappropriate methods, as the author's conclusion is doing.