Hello, 

The last year's cut off marks for SC category under state quota was 250-400 in range for government medical colleges. If v refer the last year's cut off marks then yes, your son has a very good chance of admission in government colleges in Tamil Nadu under State quota with a score of 446.

Following are some colleges in which you can apply for admission. 

Madras Medical College

Stanley Medical College

PSG institute of Medical Sciences

Christian Medical College

Madurai Medical College

Thanjavur Medical College

Tirunelveli medical college

You can apply for admission in the above mentioned government Medical Colleges under SC categor.

Good Luck.