Top Secret Clearance Question

[TexanGUY]

New guy....I am really wanting to enlist in the Navy as IT, or possibly CTN but prefer IT since I am currently in school for my AAS in Computer Networking Cisco. I have a deep desire to serve my country and secure my families future. I have seen around the web and also on this forum that IT requires a top secret clearance or secret clearance which is it?

My concern is that when I was younger I did experiment with marijuana while in highschool which was over 10+ years ago , I have no criminal record what so ever but Im just really scared I will get denied my clearance if admit to using pot in highschool. Can anyone lend some advice or have knowledge on this? I saw a similar post but the guy had a drug charge, which isnt the case for me. Should I not even say anything? Would I be denied if i was honest about it? If i get denied my clearance am I able to still back out, as I really only want a job related to what im in school for. Thanks