How to build a dynamic page?

I'm new to web development, currently, I'm creating a website that will allow students to rate their university. Since there's a lot of universities, I want to build a dynamic page to let the page load the contents from the database automatically. But the problem is, with my method(which I think is totally unusual and wrong), I can't copy the link of the school and send it to the others because the page is getting information from the previous page to load all the contents.
This is what I did on the first page

            $sql = "SELECT * FROM schools WHERE state_id=$sid";
            $result = mysqli_query($con, $sql);
            if (mysqli_num_rows($result) > 0) {
            while ($row = mysqli_fetch_assoc($result)) {
                echo"<form action='../school.php' method='post'><div class='states&school'>
                <h3><button class='searchedschool' name='id' value=".$row['school_id']."  >"
                .$row['school_name']."</button>
                </h3>
                </div></form>";
                    }
                }
                ?>

Basically, I have this PHP code to echo out the list of schools and with school_id as button value
And on the school.php page

<?php
$sid=$_POST['id']
?>
h1 class="schoolheading"><?php
                    $result = mysqli_query($con,"SELECT school_name FROM schools WHERE school_id=$sid"); 
                    while($row = mysqli_fetch_assoc($result)) { 
                        echo $row['school_name'];}
                    ?></h1>
        <div class="schoolmain">
            <div class="schoolbody">
            <div class="school_top">
            
            <?php
            $result = mysqli_query($con,"SELECT school_title FROM schools WHERE school_id=$sid"); 
            while($row = mysqli_fetch_assoc($result)) { 
               echo"<img src='image/".$row['school_title'].".jpg' class='schoolphoto' alt=''>";}
            ?>

I use code like these to echo out all the information where school_id=$sid $sid is the value I get from the previous page.
So what is the actual way to do this, so I can have an actual URL for every page?