And I don't think the techniques he used were likely all that different than what an adult man would use. It probably just boiled down to making an attempt, and her being receptive, whether by random chance or because he was her type.
The attempt itself is pretty formulaic. It boils down to, making an excuse to get together at some location that's suitable for sex, and then making a move on her, and pushing for sex.
If there's chemistry between a male and a female, then all that needs to happen is that they go some acceptable place where they can be alone, and he tries to have sex with her.
The only difference between Vili and an adult male is that he doesn't have money or a driver's license. But the same could be said for a lot of adult men who are able to get women to have sex with them. If there's chemistry, the woman will pick him up in her car, and take him to her place, if necessary. It sounds like that's what probably happened; they were found in her car.
Now, if it were an adult man wanting to get with an underage girl, then it would be more likely that he'd need to be the one providing the money, car, and place to have sex. But, usually the whole point of a woman's having her own job, such as being a teacher, is so that she has more freedom to do what she wants, whether that's buy her own shoes, or have sex with sixth-grade boys.
Probably a lot of teachers will give a student various signals (e.g. locking gazes, engaging in nonessential smalltalk, laughing at his dumb jokes, giving him favoritism that can't be explained in any other way, etc.), that they'd be interested in sex, but he disqualifies himself, thinks he doesn't have a chance with her, can't figure out how to make it happen, etc., when really, all he needed to do was follow a formula for closing the deal, which is not even all that complicated or nuanced.
But, for lack of a little knowledge or creativity, a lot of pussy probably gets left on the table.
• ( http link ) Bonecrcker #132 - Finding and Approaching Women