Despite being very old and traditional, my school also had no uniform and was very laid back when it came to our appearance. Pink hair was allowed, although flip flops weren't... I never really understood that.
We were allowed to wear makeup although it was never my priority at the time and I would spend every last minute in bed until I had to leave. If you do like to wear a bit of makeup to school I've created a simple and natural look that you can replicate.
The Dr Jart Water Fuse BB Cream is really light-weight and will wake up your skin and give you a fresh look. The Rimmel Wake Me Up concealer is perfect for 'I stayed up all night on MSN messenger' dark circles, wait does MSN messenger even still exist?! I applied the concealer on top of the Smashbox under eye primer to make sure it lasts all day.
I used the Soap & Glory bronzer and Benefit's Coralista blush, but one or the other would do! For my eyes I used my finger to apply the Maybelline Colour Tattoo in 'On and On Bronze' and then the Lord & Berry brown eyeliner, but you can leave the eyeliner (it's just a habit!). For mascara I used Maybelline 'The Rocket' which is natural enough for school but still gives great volume and curl.
If you have oily skin then use a primer first, I used the Laura Mercier one and you can also apply a bit of translucent powder to set the makeup, I used the Soap & Glory 'one heck of a blot'. A tinted lip balm is a nice way to add some colour to your lips or you can use a natural shade like the Maybelline Baby Lips in Peach Kiss.
If I was actually 15 and not 25 I could get away with less makeup, so please adapt this for your own look. It's just a guide and a bit of inspiration for a daily natural makeup look that you can wear to school or college.