All these sighs and we will do our best things are going to lead to the very fights and disappointments you fear.
There is nothing wrong with saying
1. We have $x saved now for your college. Unless we have job losses we expect that will be $Y by the time you are a senior in HS.
2. Therefore, that means about $Y/4 will be available each year for college expenses including tuition and room and board.
3. Schools that cost more would require you to get need based or merit aid.
4. We are unable to take out loans on your behalf.
My parents were poor. They told me in 6th grade they had nothing available for college. Focused me wonderfully.