Log all keyword searches?

Any idea how this works? We want to see what keywords users and putting into Google . I've gone to Log & Reports -> Security Log -> Web Filter , and it just lists sites that were blocked.  We do have SSL Interception turned on and certificates deployed. 

I just want a list of keyword searches, even better if i could get a top 10 keyword search list with Forticloud. 

I work in a school so we get asked more what has person X been searching for rather than what websites have they visited.