As suggested by above user, for legitimate school expenses, you can always send money from Nepal for total of expenses of one academic calendar year. Just like when you came for 1st time when you were allowed to bring money mentioned in your I-20 and living expenses. It will be lengthier process and all those paper work, But I think it is worth it than 'hundi' or exchange with someone here. I do not suggest doing exchange with someone that you do not know and I do not think it will work and the risk is too much. I tried once here with someone and it didn't work. However, if you know your friends or relatives or someone you can trust, you can do it too. I did with only my closed friends. Hope this helps.