Staying low, both in tackling and blocking to gain leverage is a basic football fundamental and must be taught and perfected by every player to be successful.
A friend of mine called me last night. He said his 12U team is not tackling low. They are tackling pretty good but some are having trouble breaking down and staying low to make tackles.
We talked about not all tackles will be low since they might be open field pursuit tackles when a player just needs to save a big yardage gain. He explained that his team is tackling good he just needs some more practice staying low to work on a few players fundamentals and keep everyone fundamentally sound.