I don't need quantified studies to know a class size of 15 is better than 30, because I've had and lived with both.
15 - The teachers answers ever question. By hearing all questions can find out what they're not communicating clearly and change methods.
30 - The teacher will answer 4 or 5 questions and move on. If your question wasn't covered, too bad.
15 - The teacher has more interaction, can observes more closely each student's work
30 - The teacher can't even see what many of the students have on their desk, no less keep track of each students feedback. Much easier for the kid to skate.
15 - The teachers have time to really read papers and evaluate content.
30 - The teachers can only scan papers, catch spelling and punctuation errors, but not enough time to really Analyze content.
Simple logic would tell you the same thing. Any time there are numbers, there's someone with an agenda behind them. The agenda may be benevolent, but it's there, because people don't compile this stuff for a hobby.
Even if they did, they wouldn't have access to the information in most cases. Oh, and the people supplying the information have their agenda too.
Be careful of simple numbers, they're never simple.
