Until recently it was believed that weight training did not help child

Explanation for option E is not what is mentioned in option E, please check
answer E might give you pause. Yes, there might be some health risks to weight training at such a young age and adding those tests to the study might have been helpful, but the results might have been positive as well

Hello,
I need some help here.
This is how I see it:
Choice A: says that programs will have to be home based. But arguments says government should bring in requirements. It does not say anything about school based or home based programs. Schools may allow home based programs on basis of certificate, etc.
Choice E: Shows that weight training may have negative consequences.

Choice E seemed better to me because of above reasons.

Could anyone throw some more light on this so that I can get the error in my reasoning?

Regards,
Ankit

Don't know the source of this question but it is certainly debatable. Both (A) and (E) are weakeners.
What you mentioned about option (A) is something I had evaluated too but I arrived at the conclusion that they mean to keep the program in school because they specifically say 'public schools.' If it were to be a program mandated by the Govt for kids between the ages 6 to 18 with the option of conducting it at home or school, public schools would not have been mentioned. It would have been mandated for all children. They mention public schools because the Govt. cannot interfere in the running of private schools.
Also, 'requiring' children to do weight training at home wouldn't make sense because there is no way to enforce it. In schools, one can schedule separate time for the program and ensure that kids attend it.

After reading the argument, a prephase like this should help see why A is the correct answer choices:

,- We need an answer choice that says that government should not institute the requirements because if they do they won't necessarily achieve their aim [to make children aged 6 to 18 stronger and all]...Looking at option A, it clearly states reason why instituting the requirement will not yield the intended result. It then follow up with an alternative.

Option E- The argument is not about whether these set of students will follow the requirement or not. So,the statement weakens wrong conclusion

Understanding the argument - ­
Until recently it was believed that weight training did not help children but in fact did harm and possibly stunted their growth. - General view. 
A new study has determined that weight training among children between ages 6 and 18 helped them grow stronger even though they did not gain muscle mass like adults. - Premise. 
Therefore, our government should require weight training for all children in public schools who are between the ages of 6 and 18. - Conclusion. So, what's the end objective/goal of this mandate? So the children can grow stronger. What will weaken it? If somehow we can know that even after this mandate the end result is not achieved? Yes. that would weaken the efficacy of the proposed plan. 

Which one of the following statements, if true, most seriously weakens the argument?


(A) The school year is only nine months of the year, and with children, weight training must be done on a consistent basis all year round. A home-based program is required for success. - Means that home training is the necessary condition. So, just mandating it in schools will not help achieve the end goal, which is the children can grow stronger.

(B) Since the children do not gain muscle mass, measuring their progress will be difficult without the specialized instruments used in the study. - measuring their progress is out of scope. 

(C) The study was performed with subjects from only one geographic location where weight training is more culturally acceptable. - But it could still be beneficial. It tries to play on the sampling bias but fails to address the main issue. 

(D) The gain in strength over a nine-month school year will be minimal. It takes at least a year for the children to show significant results from
weight training. - Even if minimal, if they do over the years, they can still benefit. 

(E) Children do not respond positively to government requirements and low morale may adversely affect results of any government-instituted weight training requirements. - how children respond is out of scope. Even if children resist and they also resist studying, but studying could still be beneficial. Isn't it?