Let's fiddle with the gas tax numbers.
Currently at 20 cents with 5 cents to schools. Raise by 8 cents with 2 cents going to schools. Highways net 21 cents. Schools net 7 cents.
So, if the 5 of 20 cents currently going to schools were restored to highways, the gas tax would only need to be raised by 1 cent and then indexed. The legislature then has to find a way to replace the 5 cents/gallon going to schools.
As for the fed gax tax, leave it alone since Texas gets less than it pays in.
I would suggest letting the local governments and school districts thrash that one out. Maybe they could *GASP* start charging the actual parents an annual fee to educate each kid! Oh, the huge manatee!
If I understand correctly, Texas would need another Constitutional amendment to redirect the 5 cents toward roads.
As for the federal gas tax, I would reduce it to 4 cents/gallon, targeted to new interstate projects (I-73, I-74, I-22, I-69, and so on). Then each state could make up the difference as it sees fit. JMNSHO.