I can help you with this.
First, the use of "said." It's one of the biggest pains in journalism: "said, said, said," or "says says says" over and over again. But that is unfortunately how most articles need to be written---at least, that's the policy at my newspaper.
The reason why is because the key aspect of news journalism is to remain impartial when writing. As one of my former editors once told me, "Don't tell me what happened. Show me."
The use of any word other than "said" tends to put a slant on the quote by putting your own personal interpretation on the
way it was said. They're usually descriptives. For example, consider the words "snapped, growled, teased, whined, giggled".....all descriptive. Quotes need to speak for themselves, with no flavor added by the journalist. The safest way to accomplish that is to use "said".
Take your use of "responded" in those sentences of yours. Was the senior J.C. really reponding to the freshman M.M.'s comment? Were they actually having a conversation together? Or was J.G. responding to the questions you asked? It's a bit confusing.
If you wanted to specify the quote as a response, the proper way to do so would be to say, "In response to M.M.'s comment, senior J.G. says, '........'."
And here's a bit more picking apart. What was J.G. referring to when he said "it is not that bad"? Was he referring to the actual test procedure itself, or the school's testing policy? Always word your articles in such a way as to leave no doubt. Be sure to clarify what J.G. was referring to.
I personally would also change all your "says" to the past tense "said." I think it makes for a more accurate article; just because the person said something at the time of your interview doesn't mean he's still saying the same thing now. But either way you choose to go, be sure to keep all your tenses the same. They all have to be either "says" or "said."
Now, onto the word "conversely." Was J.G.'s statement truly the converse--opposite--of what M.M. said? Is J.G. really in support of having the tests? According to the quote, he just said that the test was "not that bad." Be extremely careful with words like "conversely," unless you're absolutely sure the two sources are in direct opposition with each other. Once again, use of that word can also be considered putting your personal slant on a story, or putting words into someone's mouth. That's a fast way to get an angry phone call from a source: "That's not what I meant!" Instead of using "conversely", word the two quotes in such a way to show that the opinions differ, but are not necessarily opposite.
All right, indention. As a general rule, each person's quote needs their own paragraph. That eliminates any possible confusion caused by quotes running into each other. That selection of yours should actually be two seperate paragraphs.
Here's how I personally would edit that excerpt. Keep in mind that I'm assuming J.G. was talking about the testing policy.
“I think that parents can tell if their kids are overweight, and should not need to have a test done at school to figure it out,†said M.M., a freshman.
But according to J.G., a senior, the testing policy "is not that bad because it helps parents to keep their children healthy."
I hope that helps!