First of all, it is commendable that you want spend your free time to learn your students something about blockchain and cryptocurrency. But for start, you should pay attention to some things which are very delicate when it comes to such projects.

You say that you ask head/principal to allow few hours for your lecture, and since you work (probably) in state school, everything you do there must be approved by authorities, and parents of students would have to agree with all the extra-curricular activities.

Besides all that you also have to take responsibility for everything that is going to happen after. Some students will probably try to trade, others will try crypto gambling - some will become victims of hacking, and all of them will at the end blame you for that.

I do not say you have to give up on your idea, but you should consider each step well and pick only those students which really show sincere interest for blockchain technology&cryptocurrency.

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Not related to topic, but advice for you - I see you are good in English, but most of your post are only applications for bounty. I suggest you to try participate more in forum discussions, in this way you can also help others.