Crossing the Line, Part 1

>>> everything is coming to a head. i'm beyond terrified as to what the end is.

>>> it's the bombshell story of the bombshell who landed in serious trouble.

>> they thought something had happened that did not.

>> the nfl cheerleader who just happened to teach high school english till ugly rumors started flying.

>> do you feel like being a cheerleader sort of put a target on your back?

>> it 100% did.

>> accused of seducing a student, for months she insisted she was innocent.

>> did you have any type of sexual relationship with cody york?

>> no.

>> tonight sarah jones tells "dateline" the real story .

>> is this the truth, the final truth?

>> this is the truth.

>> revelations from investigators.

>> there are over 8,000 text messages. they actually made me blush.

>> repercussions for sarah 's own family. her mom indicted too.

>> i was in jail with my daughter.

>> plus, for the first time, her student is speaking out too, and he didn't come alone.

>> what's it like to be sitting here today as a couple?

>> i'm lester holt , and this is "dateline." tonight, " crossing the line ." here's jeff rossen .

>> reporter: with her dazzling smile and provocative moves, hard to believe this nfl cheerleader was also a buttoned-up high school english cheerleader.

>> who can tell me after looking over --

>> reporter: accused of a felony sex crime .

>> cheerleader indicted.

>> reporter: it's the story that had everyone talking this summer. sarah jones painted as a predator who took advantage of a teenage boy, one of her own students. and just last week, she faced a judge.

>> state your name.

>> sarah elizabeth jones.

>> this was not about sex. this was not about a hidden relationship.

>> reporter: so what was this about? sarah 's defense team called it a modern-day witch hunt .

>> they're obsessed, in my humble opinion, with getting her.

>> prosecutors called her a sex offender , who knew what she did was wrong.

>> the truth is going to come out, and i will bring it out.

>> reporter: we'll go inside the case, from sarah 's personal video journals.

>> i'm beyond terrified.

>> reporter: to her outright denials.

>> did you ever have sex with this student?

>> no.

>> reporter: now you'll hear from that teenage boy at the center of it all, speaking exclusively to "dateline."

>> when you heard the police are investigating, was it panic time?

>> yes. i was a nervous wreck. i would just lay in my bed and cry.

>> reporter: the juicy headlines would only skim the surface. this saga isn't just about teacher/student sex, it's about choices. sarah 's loyalty to the truth, parents loyalty to their children. their choices would take them places they never wanted to go, and certainly a long way from where it all began. sarah was born and raised in small town kentucky. her dad, tim, ran a popular convenience store. her mom, cheryl, was a long-time teacher and school principal .

>> what were you like as a kid?

>> i was a happy, happy kid. kind of -- very busy.

>> sarah , wave to me.

>> reporter: sarah grew up in a close-knit family, all devout christians. they played together and prayed together.

>> we do things as a family and that's how i was raised. that's kind of what we focused on is doing everything as a family.

>> reporter: sarah was homecoming queen and at the top of her class, and her parents were proud.

>> it was a perfection thing that i wanted to have straight as and nothing was -- i was never going to settle for less.

>> she is probably one of the most wholesome girls that you would find.

>> she was going to graduate from high school . she was going to become a teacher. she was going to get married, she was going to have kids.

>> the all- american life .

>> absolutely.

>> reporter: but when sarah turned 20, she surprised everyone. she says without telling her parents or anyone else, on a whim she tried out for the nfl's cincinnati bengals cheerleading squad.

>> i believe there were like 400 girls that tried out, and i ended up making it. i have no idea. i called my parents and said, oh, by the way, i cheer for the bengals. and they were like okay, sarah , right. not you.

>> reporter: yes, her. but between cheers, sarah was studying to build a career just like mom.

>> i absolutely could not wait to get a degree in education and start teaching.

>> when sarah came to you and said i want to be a teacher --

>> i was thrilled. i mean when your child wants to follow in your footsteps, your good footsteps, you're thrilled.

>> reporter: and right out of college, sarah scored her dream job , teaching english here at dixie heights high in kentucky. she was just 23.

>> i wanted those kids to love school, because school should be a good experience.

>> reporter: but sarah was a different kind of teacher. it wasn't just her age or personality, it was that flashy weekend job.

>> the cheerleading thing, it made me more marketable as far as from the boys' standpoint because they could talk about -- you know, on monday they could come in and talk about the game because i was there.

>> reporter: but the girls --

>> the girls were very jealous if any of their boyfriends were in my class.

>> hard to ignore the obvious. a lot of people see the skimpy outfits, the sexy poses and a lot of people see the cheerleaders as sex objects . as a mom, that bother you?

>> i just really never thought of it that way. she's my kid.

>> reporter: by age 24, sarah seemed to have it all. a career she loved and a weekend job she adored. but the good times wouldn't last long.

>> do you feel like being a cheerleader sort of put a target on your back at school?

>> it 100% did.

>> reporter: soon sarah would realize just how big that target was. in late 2009 , someone posted ugly rumors about her on the gossip website thedirty.com saying she might have sexually transmitted diseases . stds.

>> they said that i had sex with the entire bengals football squad, that i had contracted two stds from a cheating boyfriend.

>> completely false.

>> completely fabricated. not true. my name was out there as being a promiscuous cheerleader. it wasn't like you could wrubrush it under the rug.

>> and now the flood gates were open. before long sarah jones would face explosive new rumors. this time about sex with a student, and this time the police were listening.

>> so what started out as hallway whispers was about to spill outside school grounds with a full-on police investigation. soon the cops were pulling sarah out of the classroom and into the station house to interview her about the student at the center of the rumors. when we come back, how her answer to a pair of seemingly innocent questions blew the case wide open .

>> texts from you to cody?

>> no.

>> when " crossing the line " continues.