Session passing value that was not expected [duplicate]

Hello, I'm a programmer and I'm doing a system for the school that I studied, but I encountered a big problem.

              School System

<h1 id="titulo">Sistema Escolar</h1>

    <div>
        <ul id="menu">
            <a href="inicio2.html"><li>Página inicial</li></a>
            <li>Informativos</li>
            <li>Bio dos Educadores</li>
            <li>Cursos</li>
        </ul>
    </div>

<div id="lateral">

    <img src="imagens/BrasaoDoCearaPeq.png"/>
    <h4>EEEP SALOMÃO ALVES DE MOURA</h4>

    <h2>Ranking das Salas</h2>
    <ol id="ranking">
        <li>Informática</li>
        <li>Redes</li>
        <li>Edificações</li>
        <li>Comércio</li>
        <li>Secretariado</li>
    </ol>

</div>

<div id="corpo">
    <h1>Selecione o curso desejado</h1>

    <div id="primeiroAno">
        <h3>1º Ano</h3>         
        <ul>    
            <a href="cadAluno.html"><li class="informatica" onclick="<?php $_SESSION['selctcurso'] = 'informatica1'; ?>"><img src="imagens/icones/informatica.png"><br/>Informática</li></a>
            <a href="cadAluno.html"><li class="edificacoes" onclick="<?php $_SESSION['selctcurso'] = 'edificacoes1'; ?>"><img src="imagens/icones/edificacoes.png"/><br/>Edificações</li></a>
            <a href="cadAluno.html"><li class="redes" onclick="<?php $_SESSION['selctcurso'] = 'redes1'; ?>"><img src="imagens/icones/redes.png"/><br/>Redes</li></a>
            <a href="cadAluno.html"><li class="logistica" onclick="<?php $_SESSION['selctcurso'] = 'logistica1'; ?>"><img src="imagens/icones/logistica.png"/><br/>Logística</li></a>
        </ul>
    </div>

    <div id="segundoAno">
        <h3>2º Ano</h3>
        <ul>
            <a href="cadAluno.html"><li class="informatica" onclick="<?php $_SESSION['selctcurso'] = 'informatica2'; ?>"><img src="imagens/icones/informatica.png"><br/>Informática</li></a>
            <a href="cadAluno.html"><li class="comercio" onclick="<?php $_SESSION['selctcurso'] = 'comercio2'; ?>"><img src="imagens/icones/comercio.png"/><br/>Comércio</li></a>
            <a href="cadAluno.html"><li class="redes" onclick="<?php $_SESSION['selctcurso'] = 'redes2'; ?>"><img src="imagens/icones/redes.png"/><br/>Redes</li></a>
            <a href="cadAluno.html"><li class="logistica" onclick="<?php $_SESSION['selctcurso'] = 'logistica2'; ?>"><img src="imagens/icones/logistica.png"/><br/>Logística</li>
        </ul></a>
    </div>

    <div id="terceiroAno">
        <h3>3º Ano</h3>
        <ul>
            <a href="cadAluno.html"><li class="edificacoes" onclick="<?php $_SESSION['selctcurso'] = 'edificações3'; ?>"><img src="imagens/icones/edificacoes.png"><br/>Edificações</li></a>
            <a href="cadAluno.html"><li class="comercio" onclick="<?php $_SESSION['selctcurso'] = 'comercio3'; ?>"><img src="imagens/icones/comercio.png"/><br/>Comércio</li></a>
            <a href="cadAluno.html"><li class="redes" onclick="<?php $_SESSION['selctcurso'] = 'redes3'; ?>"><img src="imagens/icones/redes.png"/><br/>Redes</li></a>
            <a href="cadAluno.html"><li class="secretariado" onclick="<?php $_SESSION['selctcurso'] = 'secretariado3'; ?>"><img src="imagens/icones/secretariado.png"/><br/>Secretariado</li></a>
        </ul>
    </div>

</div>

This is the file code of the file. The problem is when the teacher is going to register a student, he has to go through this screen to select the course when he / she registers. The course is saved in the database as a secretariat. the last course, but it is not to happen, he has to click on a course and the course he clicked is to be saved together with the student. Any more experienced php programmer could help me ?? Thanks in advance for your help.