This year I have purchased GoGuardian. I'm hopeful that this will solve many of our problems. I have already locked students out of the themes feature and a few others, as well as directing all searches to safe searches. There seem to be lots of options from the admin console and with the teacher licenses, there will no longer be a way for students to hide their game playing during class.
Teachers are thrilled, students, not so much. It remains to be seen if this will really work but I am starting the year with high hopes. Now we just have to get our WiFi working!!