Here's an example on how you should do it according to your increasing level:
- starter students must use their native language / English language dictionaries.
- intermediate students must start using both their native language / English language and English / English dictionaries, as well. This way, they will force themselves to search the meanings into the studied language and start getting a high control of it.
- advanced students are not allowed to use a native language / English language dictionary anymore, unless they're searching for a new word.
On the right sidebar you will find some useful links including dictionaries... English / English ones!