My name is Mrs. Mary Kay Flynn and I teach the four-year-olds.  I have a Bachelor of Arts Degree from St. Mary of the Woods College in Special Education, and a Master of Science Degree from Dominican University in Early Childhood Education. My prior experience includes teaching kindergarten, 1st grade, and 2nd grade.  I have been at St. William School for many years and began the Preschool Program.

Children at the preschool age learn best through observation, exploration, imagination, and active participation.  To accomplish this I have created my classroom environment to be child-centered, stimulating, safe, nurturing, and developmentally appropriate.

Each child is unique and special. They learn in different ways.  As a teacher, it is my job to meet each child’s needs in order for them to become self-confident and successful learners. It’s very important to keep a line of communication going with my families. This is done through my weekly newsletter, which includes weekly activities and happenings for the upcoming week.

Pre-Kindergarten Teacher

I am Angela Koscielniak, and I am the Pre-4 teacher’s aide.  I have been a teacher’s aide for the last 18 years.  I was an aide for Kindergarten, second grade, and third grade, before moving to Pre-4 four years ago.  I assist the teacher in classroom activities and work in small groups with the children.  I helped with the Extended Day Program for many years, too.  


I have enjoyed every minute of my work with the children. I appreciate watching the children grow and express what they’re learning. I love watching their little minds at work. For the last two years, I have had the pleasure to assist with Student Council, guiding them with many different activities for the school children. 

St. William is my home parish, and I’m very involved.  I am a Eucharist Minister and I teach Religious Education. 

I look forward to getting to know you and working with you to educate your children. I also look forward getting to know your children and watching them grow in their love of learning.

Pre-Kindergarten Teacher

Hello everyone! My name is Sarah Welch, and I am the Kindergarten teacher here at St. William School. This is my first year at St. William, and my first year teaching overall. Prior to teaching, I attended Saint Mary’s College of Notre Dame where I received my bachelor's degree in Elementary Education and a minor in both Early Childhood Education and Sociology. I could not be happier to be teaching at St. William School. The warm welcome I received from the families, students, and staff here was such a blessing to me as I made the transition to St. William. I am very excited to teach Kindergarten and for all the great families that I will encounter. Kindergarten is where my heart is and I am truly blessed to have the opportunity to help children learn and grow daily. I strive to create an environment that is positive, safe and inviting while providing many opportunities to develop new skills enabling the learning experience for every child in my classroom to flourish.

Kindergarten Teacher

Welcome to first grade! My name is Madeleine O’Connor and this is my first year teaching at St. William School. Prior to this I taught as a long-term preschool substitute teacher at St. Bartholomew. I am a recent graduate of Northern Illinois University with my Bachelor’s in Education. I have a deep appreciation for a Catholic education. I attended both Queen of all Saints for grade school and Resurrection College Prep for high school. I am very thankful for the opportunity to teach first grade and appreciate the warm welcome that I received. My goal is to provide a learning environment that is welcoming, safe and positive. I want first graders to achieve their goals and have a successful school year!

1st Grade Teacher

Melissa Harris started teaching second grade at St. William School during the fall of 2018.  Prior to teaching at St. William, she taught third grade and PE at St. Luke School for five years. She served as the Curator of Conservation at the Racine Zoo for several years.  She also taught fifth grade at St. Peter in Kenosha, WI for many years.  She graduated with her BA in elementary education and a minor in psychology from Carthage College in 2000.  She earned her MA in education with an emphasis on character education and adaptive education from Mount Mary University in Milwaukee, WI in 2005.  When she is not at school, Melissa enjoys spending time with her family going to zoos, museums, and playing board games.  She is an avid cook is always experimenting in the kitchen!  Her favorite books to read are books about the Royal Family and history.

2nd Grade Teacher

Hello! My name is Clare Hulsebosch, and I am the new third-grade teacher.  I moved here from Milwaukee recently, where I taught high school English to ninth, eleventh, and twelfth graders.  I recently took a break from teaching for a year, which I used to get my master’s in school psychology. Outside of school, I love to go hiking and explore the city.  I’m really excited to be working with my third graders this year and can’t wait to see what we learn together.

3rd Grade Teacher

My name is Mrs. Judy Potempa, and 2017-2018 will mark my 10th year teaching 4th grade at Saint William School. During this year, students will participate in a variety of exciting lessons including hands-on science activities, social studies projects that connect with real-life experiences, novel studies, and math. I’m also pleased to share that a new Reading/Language Arts curriculum will be introduced to 4th graders this school year.

Technology is blended into lessons and many of our math lessons will be regularly presented on-line. Our classroom has desktop computers and a library with a large selection of fiction, non-fiction and trade books for independent reading and research. We also have subscriptions to Highlights, Ranger Rick, and National Geographic for Kids Magazines.


When students are in my classroom, they have reached an intermediate level of school. More projects, reading and writing assignments, math practice, and routine homework should be expected. 4th graders can participate in school sports, band, and continue with altar serving and choir. In order to accomplish all of our goals, we have simple rules: be on time and have all school materials ready before the tardy bell rings; listen to and follow all directions; be polite, caring, respectful, and responsible; and be a positive member of our 4th grade community by supporting all learning efforts. 

4th Grade Teacher

My name is Mrs. Colletti and I am the fifth grade homeroom teacher for St. William School. I also teach sixth grade math. My educational background includes a Bachelor of Arts degree from St. Xavier University and a Master of Education from Dominican University. I have taught various grades at St. William School and this has helped me to understand the skills that your children need as they advance through their elementary years. This year will be an adventure for your fifth grader as we learn many new things together. I believe that success happens when preparation meets with opportunity so we will do many challenging activities as well as learn how to be organized and responsible to each other and ourselves. Our day begins and ends with prayer. Our classroom will be a fun, exciting place to be as every day is a good day. I look forward to meeting all of you. 

5th Grade Teacher

Welcome to 6th grade with Mrs. Karen Zaccaria.  I also teach 5th grade social studies. My family has strong ties to the St. William Parish community with several generations of Zaccarias covering over 80 years.  Many of the Zaccarias have graduated from St. William School, including my husband and son.  The passion I have for teaching is just as strong today as it was when I first started teaching.  I have taught full-day kindergarten and first grade.  Teaching computer classes for kindergarten-8th and the school’s technology coordinator are another positions I held before my current teaching position as the 6th grade teacher.

        My teaching style combines a varied balance of experiences, from hands-on, peer teaching, project-based LEARNING, individual and group work, and performance based assessments.  I do believe that students learn in various ways; thus, I provide opportunities for students to build on his/her strengths and develop skills that need support.

        I look forward to working with you and your child this school as a team.  Please contact me if you have any questions and concerns so we can work on helping your child be as successful as he/she can be.  You can REACH me at

 Academic Degrees

  1. BA--Concordia University

  2. MA.Ed-St. Xavier University


  1. Elementary Education

  2. Elementary Education (self-contained general education)

  3. Language Arts

  4. Social Science

  5. Teacher Leader-English Language Arts

  6. Teacher Leader-Social Science

6th Grade Teacher

My name is Sandy Frobel and I am the 7th grade homeroom teacher. I also teach Science and Math to the 8th grade students. This is my 27th year educating students at St. William School. My role is to help your child reach his or her potential. I am available to students and parents any time help is needed or for any questions and concerns. My goal is to create a safe and nurturing environment for students. I expect all students to come prepared for class and strive to do their best. It is necessary for all to be respectful of everyone in the school. When students are in doubt, I would encourage them to ask for help. Students are given homework regularly which is posted in the classroom and on Edmodo and expected to complete work on time. Again, a child's education and growth are very important. I want to see your child develop in both knowledge and faith and be prepared for their future years.

7th Grade Teacher

I’m Martin Zaccaria, and I am the 8th-grade teacher for St. William School. Prior to the 2019/2020 school year, I was the Physical Education instructor for our pre-school through 8th-grade students. I earned my Bachelor’s in English Literature and Catholic Studies from DePaul University. I am also currently seeking my Master’s in secondary education at DePaul. Although I am one of the newer teachers here, my family has been a part of the St. William parish for four generations. As a graduate of St. William, I love the fact that I can work at my old school and give back to the place and people that started my education. I believe in strong Catholic schools that not only teach our children solid academics, but also instill in them a faith in Jesus Christ and active participation in the Church. In P.E., our students work through an exercise routine and then participate in a variety of sports and activities including: baseball, basketball, football, handball, lacrosse, mediation, soccer, and volleyball. In the spring, we host our Kids’ Fitness Challenge & Keeping Kids Healthy day-long event in which students learn from experts how to make healthy choices and participate in a variety of physical activities. Our students not only learn how to play various sports, they practice valuable teamwork skills and learn healthy habits.

8th Grade Teacher

My name is Terra Llanes and I have been teaching private music lessons for five years. I joined St. William School during the 2019/2020 school year. It is my first year teaching general music and physical education in a classroom setting. I graduated from North Park University with a Bachelor of Arts in Music. I also took many education courses throughout my time there. For fun I like to bike and play volleyball, and on rainy days I love to read and write fiction.

Music & Physical Education Teacher

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Chicago, IL, 60707

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