DS being bullied at school!

[MamaMoose1]

My 10 year old son is being bullied by a boy in his class, he has also bullied another boy on two occasions too. He kicked, pushed and told my son he was stupid on Friday, when they were playing football in the school field, my son still has a mark on his leg from the kick, my son told a teacher who then said they had to resolve it themselves, as the other boy denied it, which is what happened with the other boy too. He doesn't want me to speak to his teacher, as he's worried the boy will do it more, or after school, what do I do now? Respect his wishes, or go against what he doesn't want me to do and speak to his teachers anyway, but doesn't this worries me he won't then trust me to tell me stuff in the future.
Thanks for reading!