"The other kids keep bullying me."
"You shouldn't put up with it."
Is "put up with" the most idiomatic expression to use in this context?
"The other kids keep bullying me."
"You shouldn't put up with it."
Is "put up with" the most idiomatic expression to use in this context?
No, there are other phrases you could use in this context, such as "take it (from them", meaning take, or accept their treatment of you. For example, "you shouldn't take it from them". However, "put up with" balances being idiomatic, while remain well-known (the vast majority of native English-speakers will understand you regardless of age or culture.