4 Answers

Speak from the heart.

The public speech I have enjoyed the most was during a Republican Convention, Elizabeth Dole gave a speech about her husband.  She started on stage and came down to the floor to finish her speech.  I thought she was talking directly to me.  It was very simple, short, and sweet as if I was actually in her living room.  The point here is that, regardless of the topic, you must communicate and connect with the audience.  Make them feel that you are conveying the message just to them and nobody else in the room.  Keep it simple, speak slowly and clearly, and be sure to make eye contact with your audience.  Lastly, smile.

I think this is it:

http://gos.sbc.edu/d/dole.html

Enjoy!

Unless there is a tragic aspect to this topic, make sure you insert several humorous anecdotes.

ALL audiences prefer humour than dry commentary or worse; pontification. If time permits, ask a few of your student friends to tell you a unique little story or incident that would be of interest to all of your student audience (including the teacher ) Incorporate these into your speech and you'll be a hit ! ( After you practice,practice, practice before a mirror and trustworthy coach like a parent or best friend )

Good luck and let us know how you made out !

Pick a subject such as "friendship" and give your views, be funny and captive. TALK TO your audience.Speak clearly. Picture the audience in their underwear always helps.....

What a very tough subject to be given.  You could really upset the apple cart. 
I think it might be fun to use an ABC approach.  Find a nice thing to say about each person in your class, using the letters of the alphabet.  
For example,
Jason is "athletic".  He plays on the soccer team and is the best third baseman on our baseball team.  He is a good sport, too; he can laugh at himself!
Tasha is "brainy".  Sometimes she helps me with my math homework.  She explains how things go together so I learn and can do it myself.  She is a good friend.  
This way you acknowledge everyone in your class with a unique observation and kind word. What you say about your teacher is up to you!  :D
(Use L for yourself.  Say you feel really LUCKY to be part of this class with this teacher).