I too am a verified geek. I even went through high school with a briefcase and pocket protector. To compound the problem my family moved very frequently (attended 13 public schools, from 21 addresses, in the 12 years from 1st to 12th grade). Consequently I seldom even bothered to try making friends. Giving presentations on any subject other than computers was the nightmare to be avoided at all costs. As you have deduced, in high school that option just will not be viable.
At one school (junior high in my case) I had an instructor who recognized my predicament and suggested that I give the school's Toastmasters club a try. It was the mathematics teacher, who also taught some computer classes, which I wasn't able to take. If it had been an English instructor or almost any other subject I probably wouldn't have even paid attention, let alone consider it. As a fellow nerd I did give his suggestion some thought and decided it couldn't hurt. The club met at a time that didn't interfere with my computer access window, so it was spare time anyway.
Glad I am that I did go there. That was the most fruitful semester I've ever connected with any school, and it was an extra curricular activity, not even a class.
The biggest part of what you can learn from them is how to gain confidence in speaking. The members of the club may, or may not, become friends in some fashion, but a friend or not, they will not hesitate to call you out for doing things you shouldn't when speaking. At the same time, they will support you and encourage you, giving advice useful to you because they will see you as you are now, and can help you get to where you want to be. And with your likely career path, speaking is probably going to be a significant part of your professional life.
A couple, possibly helpful, pointers for immediate use, with or without Toastmasters. Learn the material that you are going to present well enough that you don't need notes to give the lecture. That's not the same as memorizing the speech, however, it's truly knowing the material. Your note cards are the plan for the presentation, not the text of the presentation. You can write the speech, in several drafts if you wish, using the skills you probably learned for writing essays in English. That will help you focus on what you know, and what you need to learn, to present the material properly. It also helps to organize the material in a manner that is proper for a presentation rather than an informal chat with a group of friends. (you know, the 3-part plan: tell them what you will tell them; tell them what you said you would tell them; tell them what you told them.)
Now that you've researched the subject properly, planned the speech, and done all the prep work, including the audio/visual aides, you are technically ready for the presentation. Most of that is likely close to what you would do anyway. Maybe more explicit, but not unique. However, it forms the groundwork for dealing with the real problem you've expressed. Having done all the research, you now know more than anyone else, except possibly the instructor, about that subject. Anyone who pays attention to your presentation will learn something they didn't already know. You are now the expert, and as the expert, you have the authority to speak. You cannot require that they listen, but you will know it is their loss, not yours, if they don't.
None of this means that you may not still be nervous, you may always be nervous when giving a presentation. Even once you are five times your current age. That is acceptable. The audience will not care that you are nervous once they realize that you know what you are talking about. Also, once you get started with the presentation, you will also forget that you are nervous. Instead, you will be focused on the material, and your nervous behaviors will become less, and bother you less. You cannot reliably fake confidence any more that you can reliably fake knowledge, so don't try to do either. Get the knowledge and have confidence in the facts, and then you just become the delivery system for the information.
Ok, enough rambling. Seriously, get in a Toastmasters club, somewhere, and you'll never regret it.