I have a 10th grader and a 6th grader in the DFW northern burbs, and we recently did a check on total cost of attendance (tuition, fees, room, board, etc) for a Texas HS kid at the major public schools in our general vicinity, i.e. A&M, OSU, OU, Arkansas, etc. We're in Plano West, and the Top 10% rule is driving a ton of smart kids to OSU, OU, and Arky. As long as the kid has a decent GPA and decent test scores to qualify for scholarships at the OOS schools designed to bring out-of-state tuition closer to in-state, they all basically ranged from high $20's to low $30's. I think A&M was $28k. OU was the most expensive with the highest bar for the types of scores needed for a better scholarship. I think it was closer to $35 if you had decent scores.
We did the old Texas Tomorrow Fund that was shut down the year my oldest was born (I signed up when she was a baby and paid $17k), which will cover 128 hours of tuition and fees at an in-state TX, or would currently reimburse at about $330/credit hour if went OOS or private (you get reimbursed the current average tuition/fee rate at a public TX senior university if you go private/OOS). With my youngest, I'm doing a 529 with the goal of having $60-70k, so basically half.
With both, I'll cover anything remaining with regular savings. My wife is an accountant that has been a stay-home-mom for 14 years, and our plan also includes her doing some seasonal tax work so that we won't actually really deplete anything.