An easy way would be to store the student data and if they are present or absent in the same state.

Each student could have an id in order to identify him easily. A function could go through the student state array and identify with the id which student was marked absent or present.

const data = [
    { id: 1, firstName: 'John', lastName: 'Doe', absent: false },
    { id: 2, firstName: 'Jane', lastName: 'Doe', absent: false },
];

const StudentList = () => {
    const [students, setStudents] = useState(data);
    const updateAbsent = () => {
        const absents = students.filter((student) => student.absent === true);
        console.log(absents);
    };
    const handleToggleAbsent = (toggleStudent) => {
        setStudents((prevStudents) =>
            prevStudents.map((student) => {
                if (student.id !== toggleStudent.id) return student;
                return { ...student, absent: !student.absent };
            })
        );
    };

    return (
        <div className="attendance-today-container">
            <h1>Daily attendance</h1>
            <table>
                <thead>
                    <tr>
                        <th>First Name</th>
                        <th>Last Name</th>
                        <th>Absent?</th>
                    </tr>
                </thead>
                <tbody>
                    {students.map((student) => {
                        return (
                            <StudentItem
                                student={student}
                                key={student.id}
                                onToggleAbsent={handleToggleAbsent}
                            />
                        );
                    })}
                </tbody>
            </table>
            <button onClick={updateAbsent}>Send</button>
        </div>
    );
};

const StudentItem = (props) => {
    const { student, onToggleAbsent } = props;
    return (
        <tr>
            <td>{student.firstName}</td>
            <td>{student.lastName}</td>
            <td>
                <label className="switch">
                    <input
                        type="checkbox"
                        onClick={onToggleAbsent.bind(null, student)}
                    />
                    <span className="slider round"></span>
                </label>
            </td>
        </tr>
    );
};

export default StudentList;

The concept is along the lines of what Sheik Yerbouti suggested and what SamiElk has demonstrated.

Take the array of student objects and add a property called absent to each and set it to false by default. Then have the corresponding check boxes toggle the absent properly for each student based on the index of the the object in the array AND the present value of its absent property. I have created a function called getData that will simulate your API call to get the student data. Here is the code:

import { useEffect, useState } from "react";
import "./styles.css";


const getData = () => {
  return new Promise(resolve => {
    resolve([{firstName: "John", lastName: "Marks"}, {firstName: "Garry", lastName: "Nelson"}]);
  })
}

export default function App() {
  const [students, setStudents] = useState([]);

  const markAbsent = (i) => {
    setStudents(prev => 
      prev.map((s, index) => ({...s, absent: i === index ? !s.absent : s.absent}))
    )
  }

  useEffect(() => {
    getData()
    .then(data => {
      data = data.map(i => ({absent: false, ...i}));
      setStudents(data);
    })
  }, [])

  return (
    <div className="attendance-today-container">
      <h1>Daily attendance</h1>
      <table>
        <tr>
          <th>First Name</th>
          <th>Last Name</th>
          <th>Absent?</th>
        </tr>
        {students.map((student, i) => {
          return (
            <tr>
              <td key={i}>{student.firstName}</td>
              <td>{student.lastName}</td>
              <td>
                <label class="switch">
                  <input
                    type="checkbox"
                    defaultChecked={student.absent}
                    onClick={() => markAbsent(i)}
                  />
                  <span className="slider round"></span>
                </label>
              </td>
            </tr>
          );
        })}
      </table>
      <button onClick={() => false}>Send</button>
    </div>
  );
}

Note that I am not certain what the Send button is supposed to do so I left it non-functional. Here is a Sandbox link for you to play with.