How to learn to swim without cles?

im in 7th grade and were gona start having swimming soon so how can i learn how to swim i dont wnat to take cles cuz im embarrased to go to take cles with kids who are like 7 and they can swim but im 13 almost 14 ohh and i can swim a little but not that well to go to the experts pool so i need to learn to swim before the summer so how to swim?????