A typical schedule is 3-4 courses per quarter. It looks like most UCSC courses are 5 credit units, so 3 such courses would make a full load of 15 units per quarter (which would add up to the 180 needed to graduate in 12 quarters (4 academic years)).
Sample first year schedule:
Q1 Q2 Q3
Math 19A* Math 19B* CompE 16
CS 12A CS 12B other course
CS 12L (2) CS 12M (2)
<h2>other course+ other course+ other course</h2>
17 units+ 17 units+ 15 units
<ul>
<li>Math 11A-11B or 20A-20B may be substituted.</li>
<li>Assumes other course is 5 units.
Slower paced introduction to CS if he has little experience:
Q1 Q2 Q3
Math 19A* Math 19B* CompE 16
CS 5J CS 11 CS 12B
CS 12M (2)
<h2>other course other course other course+</h2>
15 units 15 units 17 units+
<ul>
<li>Math 11A-11B or 20A-20B may be substituted.</li>
<li>Assumes other course is 5 units.
Faster paced introduction to CS if he has more experience:
Q1 Q2 Q3
Math 19A* Math 19B* CompE 16
CS 13H other course other course
CS 13L (2)
<h2>other course+ other course other course</h2>
17 units+ 15 units 15 units
<ul>
<li>Math 11A-11B or 20A-20B may be substituted.</li>
<li>Assumes other course is 5 units.
It does look like some of the other possible courses associated with the residential college are 2 or 3 units, so one or two of those would be used to round out a quarter where he needs a 2 unit lab (CS 12L, 12M, or 13L) to make a 15 or 16 unit quarter instead of a 17 unit quarter.
If he earns a high score on the AP calculus AB exam, he may be able to skip Math 19A (see https://ua.soe.ucsc.edu/advanced-placement ), but it is best for him to try the old Math 19A final exams (some linked from https://people.ucsc.edu/~eastman/Math%2019A%20-%20Winter%202017/19AhomeW17.html ) before deciding whether to skip.