I’d like to juxtapose two sets of verses from the New Testament of the Bible to delineate the character of a teacher and his pupil:
Acts Chapter 5 poignantly portrays Gamaliel based on a situation where Peter and other Christians preached Jesus, thus:
34 Then stood there up one in the council, a Pharisee, named Gamaliel, a doctor of the law, had in reputation among all the people, and commanded to put the apostles forth a little space;35 And said unto them, Ye men of Israel, take heed to yourselves what ye intend to do as touching these men.36 For before these days rose up Theudas, boasting himself to be somebody; to whom a number of men, about four hundred, joined themselves: who was slain; and all, as many as obeyed him, were scattered, and brought to nought.37 After this man rose up Judas of Galilee in the days of the taxing, and drew away much people after him: he also perished; and all, even as many as obeyed him, were dispersed.38 And now I say unto you, Refrain from these men, and let them alone: for if this counsel or this work be of men, it will come to nought:39 But if it be of God, ye cannot overthrow it; lest haply ye be found even to fight against God.
At Acts 26 Paul testifies about himself thus:
9 I verily thought with myself, that I ought to do many things contrary to the name of Jesus of Nazareth.10 Which thing I also did in Jerusalem: and many of the saints did I shut up in prison, having received authority from the chief priests; and when they were put to death, I gave my voice against them.11 And I punished them oft in every synagogue, and compelled them to blaspheme; and being exceedingly mad against them, I persecuted them even unto strange cities.
So this is what Paul did, by his own admission. He persecuted the Christian believers and even went to the extent of getting them death sentence. Paul says ” he compelled them to blaspheme”! 
So why did Paul do these things? 
He says at Philippians 3:6 thus:
Concerning zeal, persecuting the church; touching the righteousness which is in the law, blameless.
At Acts 22:3, Dr. Luke says that Paul spoke thus:
3 I am verily a man which am a Jew, born in Tarsus, a city in Cilicia, yet brought up in this city at the feet of Gamaliel, and taught according to the perfect manner of the law of the fathers, and was zealous toward God, as ye all are this day.
So Paul was brought up as a student of the same Gamaliel referred to above. Gamaliel cites two examples and arrives at the conclusion that both Theudas and Judas of Galilee had declared themselves to have been more than mere mortals, yet their end showed that they were mere mortals who had their time in the sun for a while and faded into oblivion. But at the same time Gamaliel cautions the Jews that, if what the Apostles said about Jesus were to be true, why take the unwarranted risk of opposing God? 
Despite Paul having been schooled by Gamaliel, while Paul was still Saul, he did not imbibe the moderate attitude of Gamaliel. 
The difference between Gamaliel was this: while Gamaliel did NOT want to be wrong; Saul believed that his belief was True and hence not only asserted his beliefs but defied anyone who went against his Pharisaical upbringing. 
Saul of Tarsus wanted to find the Truth and took those beliefs to the extremes! 
I believe Gamaliel was able to impart knowledge but NOT THE WISDOM, which made Saul of Tarsus do the things which he did against the Believers in Christ. 
Saul had a gory past, which along with his oft repeated accomplishments as a human being, stickler to the Mosaic law, being a Roman citizen and thus entitled to certain privileges, is interspersed. Naturally he has to glorify the Grace more than Jacobean ‘Works’, along with Peter, whose imperfections are well documented. 
In Christianity there is an inherent conflict between WORKS and GRACE and if one examines the putative lives of the votaries of each, the past life of each of the votaries has a significant bearing. 
Had Gamaliel been converted to Christianity, as I presume there is nothing contrary to that assumption of mine from the Bible, I believe that Gamaliel would have rooted for the WORKS a trifle more than GRACE. But why Gamaliel was not the recipient of such an epiphany as Paul on his way to Damascus, depends on how virulently one takes an ideological position. In Gamaliel’s life there was Liberty, but Saul of Tarsus not only bound himself with the Mosaic law but also virulently imposed it on others and worse still inflicted punishment on those who digressed. This virulence called for course correction and the epiphany happened. Moderation is the foundation of Liberty, methinks⚖️