The age should not be lowered for a number of reasons, but here are two.
1. Typically, most teachers in high schools are "leftists", and despise anything on the right. This comes through in their teachings. In my kids schools, the teachers consistently blasted the Tories, until I complained to the school system. The teachers are free to have their own opinions, but they are not free to bring their biases to the school system. The same holds true for any right leaning teacher, but man, these are hard to find.
2. Most students, high school and post secondary, are by nature left leaning, thinking they can change the world, etc. While this attitude is admirable and is to be encouraged, once reality hits, this attitude changes as the students become taxpayers and become aware of how their hard earned tax money is being spent. In addition, the maturity level of most high school students is not very high, and again, this is okay. Most students main purpose in life is to get decent grades and to find a date for Friday or Saturday night. Nothing wrong with that at all, and I firmly think that kids should be allowed to be kids. But kids are just that: kids. They have not developed life skills yet, and until they can pay the mortgage their parents pay for, until they have their own vehicle they have paid for, and until they pay taxes, utilities, etc., they have no idea of what the cost of living actually is. You will find that many students are NDP supporters for one simple reason: The NDP supports totally free post secondary tuition. Great idea, but somebody has to pay for it, and it sure as hell ain't the students.
Just my thoughts on this issue.