We started at 8:00, and got out at 3:15.
Though when I was in high school I sometimes took early bird classes so I started at 6:00 and got out at 2:10. Or I would arrange to have my study hall as my last hour so I could go home early. The best year was when I had outdoor adventure class (wall climbing, outdoor ropes climbing, etc...) as 6th hour, and study hall 7th hour (my last hour so I could go home). Easy and very fun class followed by going home made for a good afternoon.
anyway, back on topic. Good luck with your snake!