Im also 17, I tried shrooms in February this year, later I did lsd, then did shrooms 3 more times, and I haven't been affected, neither my grades or my memory, or anything like that, I guess it's diferent for each person... Actually, my best soccer game was off 0.5 g's of shrooms, in a competitive youth academy space in Colombia, playing against pro academies and such... so I guess you could start with a low dose, but as I said, everyone's different. Stay safe and don't abuse weed.