I'm a CTO of a company with 700 employees.
I had terrible grades in high school. I didn't do any homework, and I focused on things that were entertaining to me instead of concentrating on school work. This was in the early 90s before the internet was huge, but I was big into computers and networking. I did run my own BBS out of my house (with 16-phone lines) and I spent a lot of time on that and with drinking / hanging out with the people I met in that community. I was lucky that I was able to graduate high school on time.
College was a disaster for me. I scheduled almost all morning classes, but it was a big partying time in my life so I rarely actually attended them. I stayed in town for college, but I moved into an apartment with some friends. We removed all the shelves from our fridge and just had a Keg in there, that we replaced about every 3 days. After 2 years of this I was suspended from college for a low GPA.
After that I figured I could just get some networking certifcations and get a good job. I decided to get a Novell certification. I already knew a lot about computers and networking from my hobbies growing up, so this came very naturally to me and I actually enjoyed it. After about 4 months of studying and test taking, I had CNE. I then started to apply to any computer job I could find and I eventually got hired by a local Network consulting compnay for about $15/hr. I loved working there. I still loved to party, so I would never get to work on time, but I would stay until 9 or 10 every night working on things and learning things. Within a year there I was the top biller in that company.
I loved working for that company, and I was great at what I did. The company that I currently work for was one of my clients. They gave me an offer that essentially doubled my salary and I've been leading their IT and Automation departments ever since.
Everything worked out great for me, and I use my experiences to try to find people that are similar to me to hire. College degrees (and certainly grades!) don't matter to me that much when I look at applicants, I just care what your knowledge level is, what your capacity to learn is, and how compatible you will be with my staff.