A good introduction paragraph depends on your prompt. Since you did not post your prompt, I cannot specifically help you, however, I can help you on a rhetorical level, at least, to some extent.
An introduction paragraph, in HIGH SCHOOL, is expected to have:
A strong thesis
Supporting Ideas
A quick summary of what you plan your paper to have.
Now, keep in mind, if this is High School level, you need to write on a college approach. Many teachers (at least, mine, as I took all AP classes throughout High school) will count off for inadequate use of grammar, rhetorical devices, or flow/smoothness/thought process.
Another point to keep in mind: An introductory paragraph is exactly what it sounds like. An introduction. It serves as an introduction to the READER, in the sense that you must capture the readers attention in the very first line. Make it dramatic. It is an introduction to the ESSAY, meaning ANYTHING you want to include in your essay NEEDS to be summarized in that introduction. It also needs to be extremely smooth, precise, and show that you don't have the attention span of a 2 year old (despite many of us teens actually having the attention span of 1 year olds).
What should you avoid?
First things first. Unless the prompt asks specifically what YOU think about something, or what YOU feel after reading a selection, or a memory that YOU have, do NOT ever use the word "I" in an essay. Do not use any first person words at all. ALWAYS speak rhetorically. If you come across a situation where you need to use "we", simply substitute it for a more professional word that refers to the masses. In an american history class, for example, when one says "we", it's usually referring to either the world, or Americans. You can sub this out for something like "The people", "The citizens", "Americans", etc.
Also, never use the words "In my opinion". This is incredibly unprofessional and will immediately turn any critical reader away from your paper simply because saying "In my opinion" makes you look as though your information came from wikipedia (in other words, it'll make you seem like you don't know what you are talking about and/or are uncertain of the validity of your own information.)
Now, to note:
Your first sentence in your intro paragraph does NOT have to be your thesis. It is recommended, however, your thesis can also come in the SECOND sentence.
Your thesis should generally be one sentence long, however, two is acceptable. (Make sure you clarify this in a note somewhere below your finished essay, if you go with a two-sentence thesis that does not start with the first sentence.) Your thesis can also be however long you need it to be. One-two sentences may be the limit, however, the beautiful thing about English is we have colons and semicolons! Don't overuse these, however, if you have a lengthy prompt and a lengthy thesis, this'll help.
I recommend writing your essay, then going back and highlighting all rudimentary words. Any word in your essay that you feel you can replace with a different/better word, do this. Google that word, and look up synonyms for it. If you find any that appease, you, great! Just make sure you use each word in the correct context, and if you are not sure, ask for help or leave it be and move on.
Hope this helps!
~Troy