As students, they don't have to focus on investment because there are more important things for them to do. Learning, finishing their education course and getting a degree which are all more important for them at this period in their lives.
Students can do both investment (if they have the money) and learning at the same time so I do not think that attending school is an excuse to not invest in any good investment venture. I am with @OP when he stated that instead of burning money on smoking, it is much better if these students are informed about a possible investment venture that can yield them a good profit in the future. These investment can give these kids a headstart after they had graduated since they may have a good enough fund to support them on their wanted venture.
Lives are so long for them to start investment anytime and opportunities are always there in the market. When they get a degree, find a job, get salary, they can have savings for investment, it is never too late.
I disagree, life is not that long and opportunities missed are hard to come by again. The same thing with the price of Bitcoin when it was on its earlier days. Besides, investing on something does not need a person to fully spend his whole day every day on it like when investing on BTC, they just need to buy and secure the wallet holding the BTC and wait for the day it hits their target price. So they can still focus on their study after their investment in Bitcoin.