March 30, 2011

High School GPA versus College Success

A while back I stated my opinion that you shouldn't bother going to college if you can't at least get B's in high school.   I still stand by that generalization.   If the best you can do is barely squeaking by as 'average' in high school then you'll very likely struggle to pass in college.    If you were below average in high school, I think that rather than jumping into college you'd be better off finding employment and working for a year, going to a skilled trade, possibly joining the military or simply taking some time to decide what is best for your future.   Of course there are exceptions and a small portion of students who do poorly in high school may go on to achieve success in college.   There were a couple replies to that original article from people who disagreed with me because they were poor students in high school but were able to succeed in college.

Am I right in making a generalization that most C high school students struggle in college?  It seemed to me a fairly safe assumption that if you struggle in high school you'll struggle even more in college.  Sometimes though such assumptions can turn out to be false so it is best to look at actual data to validate the idea.  Today I'll dig into that data a little more to explore the correlation between grades in high school and students success in college.

Today's C is the new D
First off lets start out with some perspective of what a C average in high school actually means today.  C grades in high school are typically not 'average' as they may have been thought of in the past.  The vast majority of college freshmen got A's and B's in high school.  According to census data on college freshmen almost half (48%) of the students entering college had high school GPA's in the A- to A+ range.   That would mean the median high school GPA for college freshman is around 3.4 to 3.5 range give or take.    Another 47% of students had high school GPA's in the B- to B+ range.   Only 4.5% of entering college freshmen in 2009 had high school grades of C or lower. By comparison 30 yeas ago in 1980 about 15% of entering freshmen had C or worse high school grades.

First a study tying high school grades to college success

I found a report titled Predicting Different Levels of Academic Success in College Using High School GPA and ACT Composite Score. ACT Research Report Series  that looked at the correlation between GPAs received in high school by students and the college GPAs achieved by the those same students.   They looked at over 200,000 students and tracked their grades in college and compared them to their high school GPAs.  Theres a fairly good correlation between high school GPA and college GPA.

For students with high school GPA's of 2.0 the probability of getting a college GPA of 2.0 or better is about 0.5, so around half the C students  in high school do better or worse than C in college.   The probability of C students getting a 2.5 or better in college drops to 0.2 and the probability of 3.0 in college is down to just 0.05.   To put that another way 95% of students who got C averages in high school do not achieve B average or better in college.   Keep in mind that this is any and all colleges so we're not talking about Harvard.   We're talking about getting B's in any college in general.    Of course there are exceptions and about 5% of the C students in high school go on to get B or A grades in college.

Figure 2 in the report on page 17 is a graph showing the relationship between high school GPA and college GPAs.   Here is that same data in table form :

High School GPAs
College GPA 2.0 2.5 3.0 3.5 4.0
2.0 or better 0.50 0.65 0.75 0.90 0.95
2.5 or better  0.20 0.40 0.60 0.75 0.85
3.0 or better 0.05 0.15 0.30 0.50 0.75
3.25 or better 0.01 0.05 0.13 0.30 0.60
3.5 or better 0.01 0.02 0.08 0.20 0.47
3.75 or better 0.01 0.01 0.01 0.08 0.30

The columns are the high school GPA obtained and the numbers are the probability of achieving the college GPA for each row.  For example if you look at the top and find the column for 3.5 high school GPA then the chances of getting each of the college GPAs on the far left are given by the numbers.   They have a 0.90 chance of getting over 2.0 in college, 0.75 of 2.5 or better, 0.5 probability for 3.0 or better college grades etc.

Second study from Back in "the olden days"

I also found a smaller paper from 1958 titled the Correlation of High School and College Grades t from the American Journal of Physics that looked at the correlation between high school grades in math and science and the grades in college.   Table 2 in that paper presents the relationship between high school grades in math and the first year math course grades in college for 238 students:

College math grade
High school grades below 2.0 2.0 to 2.4 2.5 to 4.0
A 17% 14% 69%
B 37% 25% 38%
C or D 71% 13% 16%

You can see a high correlation between high school grades and college grades.  Most students who got C's or D's in high school went on to get C's and D's in college.   However you can see that theres still 16% of the students who had C or lower in high school but ended up with B or A grades in college.     Only 12% of the students in the sample had A grades in high school while 40% had B's and 48% got C's or D's.    In this group at least back in 1958 the C grade was more of a true average or median grade with about half students getting above C and about half getting C or lower.   If you took that group of students from 1958 and put them in a school today I would expect that many of the kids getting C's back in the 50's would be getting B's or even A's today. This is an important detail that we should keep in mind that grade inflation has made a C grade level today far worse than what a C from decades past represented.   

One More Study on the Topic

I also found the article with the lengthy title of  "VALIDITY OF HIGH-SCHOOL GRADES IN PREDICTING STUDENT SUCCESS BEYOND THE FRESHMAN YEAR: High-School Record vs. Standardized Tests as Indicators of Four-Year College Outcomes"   (via google)   That one is from the University of California system study of about 80,000 students.  

It says pretty bluntly :

The study finds that high-school grade point average (HSGPA) is consistently the best predictor not only of freshman grades in college, the outcome indicator most often employed in predictive-validity studies, but of four-year college outcomes as well.

However I should point out that the U.C. system is pretty selective and most of the students admitted are in the top 10% or so of the graduates in California.   It doesn't really relate to 'C' students since they can't usually get into U.C. schools.   I do think though that their general conclusion that high school grades are a good predictor of college success is useful to see.

Bottom Line : The data I found confirms my belief that a C student in high school today has a very low chance of obtaining good grades in college. 

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