First, before changing tone, identify clearly what the bold words are saying. The tone here is semi-positive; it's a little more positive than neutral. Clearly what the bold words indicate is that a well respected student scholar received admirable marks on their (non-gender singular "their")assessments of academic achievement.
In order to make a boldly positive tone, the degree of respect and admiration must be increased. Similarly, a negative tone requires a significant reduction of respect and admiration. Start with synonyms.
Smart: some of the many synonyms are acute, astute, egghead, crafty, clever, bright, fresh, shrewd, keen, and ingenious. Some of these that lead to positive tone might be clever and bright. Some that lead to negative tone might be egghead and shrewd.
Grades: some synonyms are level, mark, rung, standard, degree. Choices here are fairly neutral; almost any synonym listed here can be used with either positive or negative tone (see more synonyms at thesaurus.com). A choice for a more positive tone, though, might be mark or level. A choice for a more negative tone might be rung or standard.
Received: this verb means, among other meanings, to have bestowed or conferred. These are synonymous meanings. Other synonymous words or phrases are to be burdened with or to sustain, accept, acquire, collect, derive, draw . A choice for a more positive tone might be conferred or bestowed. A more negative tone might come from draw or burdened.
Student: some synonyms are amateur, beginner, neophyte, probationer, scholar, abecedarian. A positive tone might come from scholar, while a negative tone from probationer, abecedarian, neophyte.
Negative tone example: The shrewd probationer drew good marks.
(More on most of these at thesaurus.com)