How to check the age from input and perform the appropriate conditional statement?

I'm taking steps back to relearn my foundations on javascript (and realizing that it's a lot shakier than what I've thought). Maybe I just need fresh eyes, but I'm not seeing where the error lies in the code.

( Lot of the things I've read online when I tried to search for answers already had a given age ie. var age = # for the conditionals, but not where it varied based on user input. )

Your help is greatly appreciated! Thank you in advance!

const ageInput = document.querySelector("#ageInput");
const paraContent3 = document.querySelector(".paractice3-p");
const enter = document.querySelector(".enter");

function checkAge() {
  const age = ageInput.innerHTML;
  if (age < 10) {
    paraContent3.innerHTML = "You would roughly be in elementary";
  } else if (age < 14) {
    paraContent3.innerHTML = "You would roughly be in middle school";
  } else if (age < 18) {
    paraContent3.innerHTML = "You would roughly be in high school";
  } else {
    paraContent3.innerHTML = "You're out of school!";
  }
}

enter.addEventListener("keydown", function (e) {
  if (e.target == 13) {
    checkAge();
  }
});

#practice3 {
  display: flex;
  flex-direction: column;
  text-align: center;
}
#practice3 h1 {
  text-transform: uppercase;
}
#practice3 input {
  text-align: center;
  width: 30%;
  position: relative;
  left: 50%;
  transform: translate(-50%);
  padding: 10px;
  text-transform: capitalize;
}
#practice3 .enter {
  text-transform: uppercase;
  width: 20%;
  padding: 10px;
  margin-top: 10px;
  position: relative;
  left: 50%;
  transform: translate(-50%);
}

<section id="practice3">
  <h1>what is your age?</h1>
  <input id="ageInput" type="number" min="1" placeholder="enter your age">
  <p class= "practice3-p"></p>
  <button class="enter">enter</button>
</section>