yep everyone is right. the only control you have over classes your 4dig semester is if you validate or declare a major early. however, if you go talk to your AOCA (air officer commanding - academics) they can normally work wonders. they're you're academic advisor until you declare a major, then you get another one.
each semester has 40 M days and 40 T days. Each semester has 4 "Go's", or 4 blocks that are 10 lessons long. Normally, PE Classes are 1 Go (ie, physical developement and boxing only last ~10 lessons). So last semester, i had PD during D go (the final Go for the semester- lessons 31-40) and this semester i have boxing H go, again, the final go of the semester (31-40).
classes are scattered throughout your days..M days, i've only got 3rd and 4th period (until H go, then i'll have 1-4 because of boxing), and intramurals 7th. T days, i've got 1-6, mainly because chemistry and physics are double periods (you dont HAVE to stay unless you have a lab or something, but MOST people stay just to get everything done early and to get help)
If you're in 1st or 2nd group (squadrons 1-20), intramurals are on M days. if you're in 3rd or 4th group (squads 21-40), intramurals are on T days. there arent any intramurals on fridays.
VALIDATION IS GOOD! dont let anyone tell you NOT to validate. if you validate but find yourself in a class that's tooo hard, you can ALWAYS get help, and nearly always you can drop into a course that's right below it. you'll have more opportunities to take cool classes your firstie year, or even have more periods off. ALWAYS worth it to validate.
hope that's enough info
i'm sure i confused you somewhere, so ask questions!