8th grader likes 10th grader? Please read... I'm very serious.?

Now when I say I'm mature, you probably won't listen but trust me when I say I am... it's something that teachers, peers, classmates and other adults have consistently said throughout my entire life. I don't drink or smoke, but I'm very driven and I know what I want to do with myself. Most of the guys in my grade act absolutely silly... all they want to do is talk about butts and boobs and nobody is serious about a relationship... all they want to do is mindlessly hook up, which is apparently fun, but based on my experiences with it, it hurts more than a relationship, with a stable beginning and end. Anyhow, a REALLY cute 10th grader at my school (this is where my maturity will fade in your minds)... actually probably the cutest 10th grader in the school has been messaging me lately, and it's been getting kind of flirty. I've made some naive mistakes in what to say, and I don't want to sound young to him because I really like him. However, I don't want him to laugh at me for trying to sound older, judge me, look stupid/slutty... I really REALLY like him. He's repeatedly told me to talk to him more at school and stop being so shy with him. There's also been rumors going around that he's going to try to "get with me" come high school (however, I'm leaving my school for high school). I just really like him... and even if he thinks I'm young, how can I get this guy? Even if it isn't an incredibly stable relationship?