Please remember that the email address you should use throughout your university, college, apprenticeship, internship and/or job applications should be a personal e-mail address and it should look professional (not too informal). Institutions pay attention to the email addresses students use. You should NOT use the school email address, as you no longer have access to your school account after finishing school.
Writing to a college/university for the first time can be quite daunting. One of the most important aspects to bear in mind is to carry out research and check the college/university's website before contacting them. University representatives do NOT appreciate being asked questions about information available on their websites.
Additionally, please remember that in the first email, as it will be your initial contact, you should introduce yourself (including the grade you are in and possibly the curriculum you are following).