If the R squared is only 15% and considered too low be considered a low analyze the impact of the independent variable on growth?

How do I tell which variable would be the most significant by looking at the P-value?

SUMMARY OUTPUT Regression Statistics Multiple R 0.395979 R Square 0.1568 Adjusted R Square 0.09356 Standard Error 14.03423 Observations 87 ANOVA of SS MS F gnificance F Regression 6 2930.092 488.3487 2.479437 0.029888 Residual 80 15756.76 196.9595 Total 86 18686.85 Coefficient:andard Err t Stat P-value Lower 95%Upper 95%ower 95.09pper 95.0% Intercept 35.598 3.484905 10.21491 3.69E-16 28.66282 42.53318 28.66282 42.53318! Free Lunch -2.07355 4.798813 -0.4321 0.666834 -11.6235 7.476394 -11.6235 7.476394 Math Learning Lab 13.29401 4.290457 3.098506 0.002684 4.755726 5 21.83229 4.755726 21.83229 Gender 3.495197 3.088682 1.131614 0.261177 -2.65148 9.641871 -2.65148 9.641871 Teacher 1 (L) 4.549251 4.212112 1.08004 0.28337 -3.83312 12.93162 -3.83312 12.93162 Teacher 2 (K) -0.04086 4.276008 -0.00956 0.992399 -8.55039 8.468666 -8.55039 8.468666! Teacher 3 (S) -2.6949 4.296118 -0.62729 0.532257 -11.2445 5.854645 -11.2445 5.854645