Like i said b4, unless she is innocent and naive, she will not
talk to strangers on the phone.
If she consented in giving her no. to u, your 1st sms to her should
be identifying yourself. (sms 1st, dun call. ) Assure her that she
is not talking to some stalker but talking to a guy she's
interested in. Just tell her your name and say something that will
instantly remind her of u in order to identify yourself. (i am the
guy from that class..... etc.)
The best excuse to let her know why u sms her out of the blue is to
tell her the truth. (Dun ever lie to a gal u like) Tell her that u
actually wanted to be a friend of hers in sch but too shy to intro
yourself face to face, and therefore resorting to cowardly methods
such as sms. Then tell her "Hope u dun mind". Ask her for her name
politely.
Continue talking to her. Tell her interesting things abt yourself.
Dun act big, act like monkey, crack lame jokes, talk abt sex, or
talk stupid things such as "i am bored" or "whatsup lady, ur
talking to a cool dude!" or anything like this. All u need is to
assure her that u are a nice person(not clown) and sincere to be
frens wif her.
Get her talking abt herself too, ONLY after u talked abt yourself.
Such as "i am from "so and so" sec sch. How abt u?"
MIND YOUR MANNERS
RELAX AND ENJOY HER COMPANY.
The next day when u see her in sch, smile at her and say "Hi" to
her face to face. (If u dun have the guts to do that, u are not fit
to be her boyfriend.) That is, if u ignore her or anything like
that, GAME OVER.
The above are just recommendations which i tried b4 and worked. I
dun know if it will work for u, if it doesn't, dun come and bang me
ok? 
