How High can a Cessna 152 Fly?

 If you click on the green arrow you will get the answer to the question below from http://www.cessna150152.com/faqs/performance.htm
5.  How high can a Cessna 150-152 fly ? 



I was thinking that if most Cessna 150s and 152 are flying from 2500 feet to 6500 feet in altitude. (Which is also the range I mostly have flown in them especially when learning to solo in 1987) and if it takes over 20 minutes to gain altitude from 9500 feet to a potential minimum ceiling of 12,500 feet, this wouldn't be a really good plane to be flying over 9000 feet. Because of you lost altitude in the mountains and didn't have the conditions to have 20 minutes to gain altitude you likely would be in trouble.