FWIW, I'm fine with a very high risk tolerance for this. Of course, as college nears, I'd transition to safer options.
This is a bit of a weird thing to write about college saving strategies. I have written about this elsewhere, but I view high risk investments as absolutely terrible tools for preparing for college. There are a number of reasons:
1) Tax benefits range from none to moderate
2) The average time for investment growth is extremely small. 18 years is a short period to invest in, and considering that most young parents see their income grow significantly in that time, the functional average time invested tends to be closer to ~6 years. That is too short of a runway.
3) Unlike retirement, college comes once and comes hard. A down market doesn't hurt retirement investments all that much, because if you plan 20 years retirement, a market crash of 50% that takes 5 years to recover will eat into significant parts of your savings, but ultimately still leave you with half your initial investment, and that investment will grow through the post-crash recovery. The goal of an education is generally to be finished in 4 years. The heavy withdrawal rate makes this higher risk for education.
4) Education costs are really high BUT depending on choices, and location, much of the cost is potentially in cost of living (room and board) instead of tuition (For example, Suny stony brook has tuition of ~7500 a year and room and board of ~18000 a year). Tuition is a beast you cannot control, and a scary and growing one. but room and board is easily controlled - you already do so for yourself. If you are a person who has the resources to invest, or could put those together, a far more effective use of your investment might be in rentals/rental knowledge. Putting yourself in the position to potentially help your kids/nieces etc by allowing them to rent from you for either cheap or free. Saving/investing so that you can help them by putting them in the position to not pay the insane prices of student housing is a huge benefit. In some markets, students face restrictions requiring them to live with family (no worries if you own) or in dorms that massively overcharge. (and that frequently require meal plans at prices no sane person would ever willingly pay).
4A) Renting to college students is typically viewed as a low-value rent situation - the turnover is high, the students tend to be noisy, obnoxious and potentially damaging, and all of this lowers profit margins. While all of those concerns are potentially true, remember that in this case the goal is not to have a rental that is the best use of your money (or even one that beats long term stock rates) but instead one that delivers more value than that corresponding brokerage investments are likely to do on short timeframes. Plus for the optimist, if you end up really liking this, it gives you something to embrace long-term.
TLDR: I think the best high risk investment for future college is to invest in yourself and sidehustle your way into real-estate and see if you like it, especially near colleges.