教室にかばんをわすれました。it is right:)

For express "To + Place", you can use both.　へ　and に,both is right but に is more common in speaking, へis usual in writing. 

「に」 this emphasise the towards and the static result,

「へ」 this emphasise the action doing,dynamic meaning.

 i think you should use this one.

教室にかばんをわすれました。