Do you need a high school diploma to get into a technical college?

A certificate of completion is not equivalent to a high school diploma or GED, and thus will not allow you to register for community college, college, university, many trade schools, or even take out student loans - it basically says you did all the coursework but didn't complete the requirements for the diploma. If you do want to go to community college, you need to finish the diploma by passing the necessary exams. Any college class will be harder than doing this, so there's really no point in going to college if you can't finish a high school degree.