has anyone else been told they can’t have adhd bc they have good grades?

ex friend told me back in high school told me i couldn’t possibly have adhd bc i got good grades so i stashed that thought away and just carried on w my life,,,now i’ve been put on biphentin. i’ve spent the past 4 years in uni struggling more and more each year, i feel like if i sought out support earlier i would be doing better rn🙃