I agree with this. If you're passionate about it and give an interesting presentation, I don't think you'll be ridiculed. It definitely depends on your age ranger though.

I think that you should also do a report on tokusatsu in general or at least mention its origins.

Thing that you should mention is how Toho, Bandai, Tsuburaya, Ishinomori, and Saban influenced tokusatsu. Talk about how toys started to influence these shows and how writers work around them. Mention the budget of these shows and how the people behind them work around with them. The evolution of suits and how the designs are often influenced on Japanese culture and what not.

Don't listen to anyone here.
Do what you want.
Ultraman is boring as fuck, everyone already knows the history of Godzilla, there's a very distinct reason why Kamen Rider died for a full decade, and why Metal Heroes aren't a thing anymore.

You do you, and if you want to do Sentai, and not a wide, sweeping history of Tokusatsu, then do Sentai.

I sincerely doubt that anybody here is suggesting turning it into a general tokusatsu thing because they want they want to see their favorites discussed or whatever you think their motives are. It's mainly because instructors are looking for something that at least appears to be educational in some manner.

I actually did a presentation on tokusatsu in high school. I was originally going to do it on a specific series (I cannot remember which) which my teacher shot down pretty quickly.

Also, you'd be surprised at how much the general public doesn't know about Godzilla. At least not at the time I did my presentation.

If OP wants to do Sentai, then OP will do Sentai. However, most of the posters seem to agree that Toku history would make for a more engaging and educational presentation than Sentai alone. Also, I love Ultraman, but that's not important - what is important is that it played a CRITICAL role in the development of Tokusatsu. Same with the Showa Riders. But like I said, if OP only wants to do Sentai/Power Rangers, then do it.

For a Sentai-focused series, I'd start off by mentioning Power Rangers as a framing device. Then mention that it was based on a show called Super Sentai. Then say "but to understand its history, we have to go all the way back to 1975" or whatever. From there summarize Goranger - Jetman, and make sure you include Spider-man as well. At that point, talk about Zyuranger and how it was adapted to Power Rangers, and then where the series went from there. Of course, you don't have to stick to that format at all - that's just how I would do it. For a Toku-focused one, I guess you could start off similarly, by mentioning Power Rangers, but instead of going back to 1975, you'll go back to 1954.

I think a general history of tokustatsu would be better. I trust you fellow students are mature enough to listen to a talk on Sentai/Power Rangers and not give you shit about it, but I think focusing only on those two for people who don't know anything about the medium would not give a full context as to where each is coming from.

Better to do a cultural influence of Tokusatsu type of deal as opposed to a Sentai otaku presentation. More depth and will be engaging.

Even for a Power Rangers history lesson, this second paragraph is ideal. Start with a reference, then take a step back to fully explore the details. Spiderman can get it on two fronts because Leopardon helped give rise to Battle Fever Robo which would radiate outward into the inevitable concept of "Megazords", and because Stan Lee considered doing what Saban ultimately would.

^This.

I would recommend to at least start with a general introduction of the tokusatsu genre as such though, because it makes the Sentai part easier to understand, like why they film certain things the way they do, what's behind the effects and stunts and so on. It can still be just Sentai though, but giving an idea about what tokusatsu is is pretty essential imho.