Along with his classmates, he will spend the day getting to know his teachers and classmates as well as completing the important task of finding his classroom peg.
George will be dressed in a smart new uniform, comprising a navy v-neck pullover, matching Bermuda-style shorts, long red socks and black shoes.
Kate pulled out of two public engagements this week after falling ill as she did in her previous pregnancies.
Yesterday, a day after it was announced they are expecting their third child, William said Kate was well but admitted: "There's not much sleep going on at the moment."
He said: "We need Catherine to get over this first bit and then we can start celebrating. It's always a bit anxious to start with, but she's well."
The Good Schools Guide has described it as: "A big, busy, slightly chaotic school for cosmopolitan parents who want their children to have the best English education money can buy".
10 things to know about Prince George's school
1 Fees for Thomas's Battersea start at £17,604 ($31,871) a year and increase in Year 3. By the time Prince George is 13 the fees will have reached £172,116.
2 "Be Kind" is the school's top rule. Celebrating, not just tolerating difference including faiths, believe and culture, is expected of all students.
3 Leadership - the school says it wants its student to lead by example, to stand up for what they believe is right and risk making unpopular decisions.
4 Discourages 'best friends' - reportedly doesn't push this in order to stop others from having their feelings hurt.
5 Small class size - George will be one of about 20 students. Average class sizes in England are 27.
6 Ballet, French, art, drama, ICT and music will all be taught, along with the Early Years Foundation State curriculum.
7 Uniform is compulsory - pulled up red socks and navy bermuda shorts.
8 Red art smocks (£30) are compulsory, along with swim hat and PE kit.
9 School is oversubscribed and parents are urged to enrol their children at birth to get in. Wannabe students must sit an entrance test before being offered a spot.
10 Organic lunches often provided including zucchini, haloumi and beetroot stacks, leek and onion risotto, baked meatballs with cannellini beans and steamed brown and white rice.
- PA, AAP